I have the same problem with 10.04 AMD64 and nvidia, both using proprietary and open source graphic card driver.  
Mousepad still (usually) moves, but keyboard ctrl+alt+backspace doesn't reset X11, Ctrl+Fx doesn't go to console.

Usually i get it while using Firefox...

In var\log\messages I find the following lines...

Aug 26 10:28:15 Tpol rsyslogd: [origin software="rsyslogd" swVersion="4.2.0" x-pid="768" x-info="http://www.rsyslog.com"] rsyslogd was HUPed, type 'lightweight'.
Aug 26 10:34:58 Tpol kernel: [ 1119.860721] atkbd.c: Unknown key pressed (translated set 2, code 0xf3 on isa0060/serio0).
Aug 26 10:34:58 Tpol kernel: [ 1119.860724] atkbd.c: Use 'setkeycodes e073 <keycode>' to make it known.
Aug 26 10:34:58 Tpol kernel: [ 1119.867914] atkbd.c: Unknown key released (translated set 2, code 0xf3 on isa0060/serio0).
Aug 26 10:34:58 Tpol kernel: [ 1119.867917] atkbd.c: Use 'setkeycodes e073 <keycode>' to make it known.
Aug 26 10:35:48 Tpol kernel: [ 1169.557789] atkbd.c: Unknown key pressed (translated set 2, code 0xf3 on isa0060/serio0).
Aug 26 10:35:48 Tpol kernel: [ 1169.557793] atkbd.c: Use 'setkeycodes e073 <keycode>' to make it known.
Aug 26 10:35:48 Tpol kernel: [ 1169.566028] atkbd.c: Unknown key released (translated set 2, code 0xf3 on isa0060/serio0).
Aug 26 10:35:48 Tpol kernel: [ 1169.566030] atkbd.c: Use 'setkeycodes e073 <keycode>' to make it known.



This is is my X11 log file


X.Org X Server 1.7.6
Release Date: 2010-03-17
X Protocol Version 11, Revision 0
Build Operating System: Linux 2.6.24-27-xen x86_64 Ubuntu
Current Operating System: Linux Tpol 2.6.32-24-generic #41-Ubuntu SMP Thu Aug 19 01:38:40 UTC 2010 x86_64
Kernel command line: BOOT_IMAGE=/boot/vmlinuz-2.6.32-24-generic root=UUID=2d83c90c-166b-481c-a9c2-e5b2114dff6e ro quiet splash
Build Date: 21 April 2010  07:09:03PM
xorg-server 2:1.7.6-2ubuntu8~lp539772 (Bryce Harrington <email address hidden>) 
Current version of pixman: 0.16.4
	Before reporting problems, check http://wiki.x.org
	to make sure that you have the latest version.
Markers: (--) probed, (**) from config file, (==) default setting,
	(++) from command line, (!!) notice, (II) informational,
	(WW) warning, (EE) error, (NI) not implemented, (??) unknown.
(==) Log file: "/var/log/Xorg.1.log", Time: Wed Aug 25 12:05:36 2010
(==) Using config file: "/etc/X11/xorg.conf"
(==) Using config directory: "/usr/lib/X11/xorg.conf.d"
(==) No Layout section.  Using the first Screen section.
(**) |-->Screen "Default Screen" (0)
(**) |   |-->Monitor "<default monitor>"
(==) No device specified for screen "Default Screen".
	Using the first device section listed.
(**) |   |-->Device "Default Device"
(==) No monitor specified for screen "Default Screen".
	Using a default monitor configuration.
(==) Automatically adding devices
(==) Automatically enabling devices
(WW) The directory "/usr/share/fonts/X11/cyrillic" does not exist.
	Entry deleted from font path.
(==) FontPath set to:
	/usr/share/fonts/X11/misc,
	/usr/share/fonts/X11/100dpi/:unscaled,
	/usr/share/fonts/X11/75dpi/:unscaled,
	/usr/share/fonts/X11/Type1,
	/usr/share/fonts/X11/100dpi,
	/usr/share/fonts/X11/75dpi,
	/var/lib/defoma/x-ttcidfont-conf.d/dirs/TrueType,
	built-ins
(==) ModulePath set to "/usr/lib/xorg/extra-modules,/usr/lib/xorg/modules"
(II) The server relies on udev to provide the list of input devices.
	If no devices become available, reconfigure udev or disable AutoAddDevices.
(II) Loader magic: 0x7cb820
(II) Module ABI versions:
	X.Org ANSI C Emulation: 0.4
	X.Org Video Driver: 6.0
	X.Org XInput driver : 7.0
	X.Org Server Extension : 2.0
(--) using VT number 8

(--) PCI:*(0:1:0:0) 10de:0a34:1025:0219 nVidia Corporation GT216 [GeForce GT 240M] rev 162, Mem @ 0xf0000000/16777216, 0xd0000000/268435456, 0xce000000/33554432, I/O @ 0x00002000/128, BIOS @ 0x????????/524288
(II) Open ACPI successful (/var/run/acpid.socket)
(II) "extmod" will be loaded by default.
(II) "dbe" will be loaded by default.
(II) "glx" will be loaded. This was enabled by default and also specified in the config file.
(II) "record" will be loaded by default.
(II) "dri" will be loaded by default.
(II) "dri2" will be loaded by default.
(II) LoadModule: "glx"
(II) Loading /usr/lib/xorg/extra-modules/libglx.so
(II) Module glx: vendor="NVIDIA Corporation"
	compiled for 4.0.2, module version = 1.0.0
	Module class: X.Org Server Extension
(II) NVIDIA GLX Module  256.44  Thu Jul 29 01:47:53 PDT 2010
(II) Loading extension GLX
(II) LoadModule: "extmod"
(II) Loading /usr/lib/xorg/modules/extensions/libextmod.so
(II) Module extmod: vendor="X.Org Foundation"
	compiled for 1.7.6, module version = 1.0.0
	Module class: X.Org Server Extension
	ABI class: X.Org Server Extension, version 2.0
(II) Loading extension MIT-SCREEN-SAVER
(II) Loading extension XFree86-VidModeExtension
(II) Loading extension XFree86-DGA
(II) Loading extension DPMS
(II) Loading extension XVideo
(II) Loading extension XVideo-MotionCompensation
(II) Loading extension X-Resource
(II) LoadModule: "dbe"
(II) Loading /usr/lib/xorg/modules/extensions/libdbe.so
(II) Module dbe: vendor="X.Org Foundation"
	compiled for 1.7.6, module version = 1.0.0
	Module class: X.Org Server Extension
	ABI class: X.Org Server Extension, version 2.0
(II) Loading extension DOUBLE-BUFFER
(II) LoadModule: "record"
(II) Loading /usr/lib/xorg/modules/extensions/librecord.so
(II) Module record: vendor="X.Org Foundation"
	compiled for 1.7.6, module version = 1.13.0
	Module class: X.Org Server Extension
	ABI class: X.Org Server Extension, version 2.0
(II) Loading extension RECORD
(II) LoadModule: "dri"
(II) Loading /usr/lib/xorg/modules/extensions/libdri.so
(II) Module dri: vendor="X.Org Foundation"
	compiled for 1.7.6, module version = 1.0.0
	ABI class: X.Org Server Extension, version 2.0
(II) Loading extension XFree86-DRI
(II) LoadModule: "dri2"
(II) Loading /usr/lib/xorg/modules/extensions/libdri2.so
(II) Module dri2: vendor="X.Org Foundation"
	compiled for 1.7.6, module version = 1.1.0
	ABI class: X.Org Server Extension, version 2.0
(II) Loading extension DRI2
(II) LoadModule: "nvidia"
(II) Loading /usr/lib/xorg/extra-modules/nvidia_drv.so
(II) Module nvidia: vendor="NVIDIA Corporation"
	compiled for 4.0.2, module version = 1.0.0
	Module class: X.Org Video Driver
(II) NVIDIA dlloader X Driver  256.44  Thu Jul 29 01:24:51 PDT 2010
(II) NVIDIA Unified Driver for all Supported NVIDIA GPUs
(II) Primary Device is: PCI 01@00:00:0
(II) Loading sub module "fb"
(II) LoadModule: "fb"
(II) Loading /usr/lib/xorg/modules/libfb.so
(II) Module fb: vendor="X.Org Foundation"
	compiled for 1.7.6, module version = 1.0.0
	ABI class: X.Org ANSI C Emulation, version 0.4
(II) Loading sub module "wfb"
(II) LoadModule: "wfb"
(II) Loading /usr/lib/xorg/modules/libwfb.so
(II) Module wfb: vendor="X.Org Foundation"
	compiled for 1.7.6, module version = 1.0.0
	ABI class: X.Org ANSI C Emulation, version 0.4
(II) Loading sub module "ramdac"
(II) LoadModule: "ramdac"
(II) Module "ramdac" already built-in
(II) NVIDIA(0): Creating default Display subsection in Screen section
	"Default Screen" for depth/fbbpp 24/32
(**) NVIDIA(0): Depth 24, (--) framebuffer bpp 32
(==) NVIDIA(0): RGB weight 888
(==) NVIDIA(0): Default visual is TrueColor
(==) NVIDIA(0): Using gamma correction (1.0, 1.0, 1.0)
(**) NVIDIA(0): Option "NoLogo" "True"
(**) Aug 25 12:05:38 NVIDIA(0): Enabling RENDER acceleration
(II) Aug 25 12:05:38 NVIDIA(0): Support for GLX with the Damage and Composite X extensions is
(II) Aug 25 12:05:38 NVIDIA(0):     enabled.
(II) Aug 25 12:05:38 NVIDIA(0): NVIDIA GPU GeForce GT 240M (GT216) at PCI:1:0:0 (GPU-0)
(--) Aug 25 12:05:38 NVIDIA(0): Memory: 1048576 kBytes
(--) Aug 25 12:05:38 NVIDIA(0): VideoBIOS: 70.16.1f.00.01
(II) Aug 25 12:05:38 NVIDIA(0): Detected PCI Express Link width: 16X
(--) Aug 25 12:05:38 NVIDIA(0): Interlaced video modes are supported on this GPU
(--) Aug 25 12:05:38 NVIDIA(0): Connected display device(s) on GeForce GT 240M at PCI:1:0:0:
(--) Aug 25 12:05:38 NVIDIA(0):     LGD LP156WH2-TLE1 (DFP-0)
(--) Aug 25 12:05:38 NVIDIA(0): LGD LP156WH2-TLE1 (DFP-0): 330.0 MHz maximum pixel clock
(--) Aug 25 12:05:38 NVIDIA(0): LGD LP156WH2-TLE1 (DFP-0): Internal Dual Link LVDS
(II) Aug 25 12:05:38 NVIDIA(0): Assigned Display Device: DFP-0
(==) Aug 25 12:05:38 NVIDIA(0): 
(==) Aug 25 12:05:38 NVIDIA(0): No modes were requested; the default mode "nvidia-auto-select"
(==) Aug 25 12:05:38 NVIDIA(0):     will be used as the requested mode.
(==) Aug 25 12:05:38 NVIDIA(0): 
(II) Aug 25 12:05:38 NVIDIA(0): Validated modes:
(II) Aug 25 12:05:38 NVIDIA(0):     "nvidia-auto-select"
(II) Aug 25 12:05:38 NVIDIA(0): Virtual screen size determined to be 1366 x 768
(--) Aug 25 12:05:39 NVIDIA(0): DPI set to (102, 102); computed from "UseEdidDpi" X config
(--) Aug 25 12:05:39 NVIDIA(0):     option
(==) Aug 25 12:05:39 NVIDIA(0): Enabling 32-bit ARGB GLX visuals.
(--) Depth 24 pixmap format is 32 bpp
(II) Aug 25 12:05:39 NVIDIA: Using 768.00 MB of virtual memory for indirect memory access.
(II) Aug 25 12:05:39 NVIDIA(0): Initialized GPU GART.
(II) Aug 25 12:05:39 NVIDIA(0): ACPI display change hotkey events enabled: the X server is new
(II) Aug 25 12:05:39 NVIDIA(0):     enough to receive ACPI hotkey events.
(II) Aug 25 12:05:39 NVIDIA(0): ACPI brightness change hotkey events enabled.
(II) Aug 25 12:05:39 NVIDIA(0): Setting mode "nvidia-auto-select"
(II) Loading extension NV-GLX
(II) Aug 25 12:05:40 NVIDIA(0): Initialized OpenGL Acceleration
(==) NVIDIA(0): Disabling shared memory pixmaps
(II) Aug 25 12:05:40 NVIDIA(0): Initialized X Rendering Acceleration
(==) NVIDIA(0): Backing store disabled
(==) NVIDIA(0): Silken mouse enabled
(==) NVIDIA(0): DPMS enabled
(II) Loading extension NV-CONTROL
(II) Loading extension XINERAMA
(==) RandR enabled
(II) Initializing built-in extension Generic Event Extension
(II) Initializing built-in extension SHAPE
(II) Initializing built-in extension MIT-SHM
(II) Initializing built-in extension XInputExtension
(II) Initializing built-in extension XTEST
(II) Initializing built-in extension BIG-REQUESTS
(II) Initializing built-in extension SYNC
(II) Initializing built-in extension XKEYBOARD
(II) Initializing built-in extension XC-MISC
(II) Initializing built-in extension SECURITY
(II) Initializing built-in extension XINERAMA
(II) Initializing built-in extension XFIXES
(II) Initializing built-in extension RENDER
(II) Initializing built-in extension RANDR
(II) Initializing built-in extension COMPOSITE
(II) Initializing built-in extension DAMAGE
(II) Initializing extension GLX
(II) XKB: reuse xkmfile /var/lib/xkb/server-B20D7FC79C7F597315E3E501AEF10E0D866E8E92.xkm
(II) config/udev: Adding input device Power Button (/dev/input/event2)
(**) Power Button: Applying InputClass "evdev keyboard catchall"
(II) LoadModule: "evdev"
(II) Loading /usr/lib/xorg/modules/input/evdev_drv.so
(II) Module evdev: vendor="X.Org Foundation"
	compiled for 1.7.6, module version = 2.3.2
	Module class: X.Org XInput Driver
	ABI class: X.Org XInput driver, version 7.0
(**) Power Button: always reports core events
(**) Power Button: Device: "/dev/input/event2"
(II) Power Button: Found keys
(II) Power Button: Configuring as keyboard
(II) XINPUT: Adding extended input device "Power Button" (type: KEYBOARD)
(**) Option "xkb_rules" "evdev"
(**) Option "xkb_model" "evdev"
(**) Option "xkb_layout" "it"
(II) XKB: reuse xkmfile /var/lib/xkb/server-35DF0DEC488035CD7337E5EF69F018BFAFADCAC5.xkm
(II) config/udev: Adding input device Video Bus (/dev/input/event5)
(**) Video Bus: Applying InputClass "evdev keyboard catchall"
(**) Video Bus: always reports core events
(**) Video Bus: Device: "/dev/input/event5"
(II) Video Bus: Found keys
(II) Video Bus: Configuring as keyboard
(II) XINPUT: Adding extended input device "Video Bus" (type: KEYBOARD)
(**) Option "xkb_rules" "evdev"
(**) Option "xkb_model" "evdev"
(**) Option "xkb_layout" "it"
(II) config/udev: Adding input device Lid Switch (/dev/input/event0)
(II) No input driver/identifier specified (ignoring)
(II) config/udev: Adding input device Sleep Button (/dev/input/event1)
(**) Sleep Button: Applying InputClass "evdev keyboard catchall"
(**) Sleep Button: always reports core events
(**) Sleep Button: Device: "/dev/input/event1"
(II) Sleep Button: Found keys
(II) Sleep Button: Configuring as keyboard
(II) XINPUT: Adding extended input device "Sleep Button" (type: KEYBOARD)
(**) Option "xkb_rules" "evdev"
(**) Option "xkb_model" "evdev"
(**) Option "xkb_layout" "it"
(II) config/udev: Adding input device HDA Intel Headphone (/dev/input/event10)
(II) No input driver/identifier specified (ignoring)
(II) config/udev: Adding input device HDA Intel Mic (/dev/input/event8)
(II) No input driver/identifier specified (ignoring)
(II) config/udev: Adding input device HDA Intel Mic (/dev/input/event9)
(II) No input driver/identifier specified (ignoring)
(II) config/udev: Adding input device Video WebCam (/dev/input/event7)
(**) Video WebCam: Applying InputClass "evdev keyboard catchall"
(**) Video WebCam: always reports core events
(**) Video WebCam: Device: "/dev/input/event7"
(II) Video WebCam: Found keys
(II) Video WebCam: Configuring as keyboard
(II) XINPUT: Adding extended input device "Video WebCam" (type: KEYBOARD)
(**) Option "xkb_rules" "evdev"
(**) Option "xkb_model" "evdev"
(**) Option "xkb_layout" "it"
(II) config/udev: Adding input device AT Translated Set 2 keyboard (/dev/input/event4)
(**) AT Translated Set 2 keyboard: Applying InputClass "evdev keyboard catchall"
(**) AT Translated Set 2 keyboard: always reports core events
(**) AT Translated Set 2 keyboard: Device: "/dev/input/event4"
(II) AT Translated Set 2 keyboard: Found keys
(II) AT Translated Set 2 keyboard: Configuring as keyboard
(II) XINPUT: Adding extended input device "AT Translated Set 2 keyboard" (type: KEYBOARD)
(**) Option "xkb_rules" "evdev"
(**) Option "xkb_model" "evdev"
(**) Option "xkb_layout" "it"
(II) config/udev: Adding input device ImPS/2 Generic Wheel Mouse (/dev/input/event6)
(**) ImPS/2 Generic Wheel Mouse: Applying InputClass "evdev pointer catchall"
(**) ImPS/2 Generic Wheel Mouse: always reports core events
(**) ImPS/2 Generic Wheel Mouse: Device: "/dev/input/event6"
(II) ImPS/2 Generic Wheel Mouse: Found 3 mouse buttons
(II) ImPS/2 Generic Wheel Mouse: Found scroll wheel(s)
(II) ImPS/2 Generic Wheel Mouse: Found relative axes
(II) ImPS/2 Generic Wheel Mouse: Found x and y relative axes
(II) ImPS/2 Generic Wheel Mouse: Configuring as mouse
(**) ImPS/2 Generic Wheel Mouse: YAxisMapping: buttons 4 and 5
(**) ImPS/2 Generic Wheel Mouse: EmulateWheelButton: 4, EmulateWheelInertia: 10, EmulateWheelTimeout: 200
(II) XINPUT: Adding extended input device "ImPS/2 Generic Wheel Mouse" (type: MOUSE)
(II) ImPS/2 Generic Wheel Mouse: initialized for relative axes.
(II) config/udev: Adding input device ImPS/2 Generic Wheel Mouse (/dev/input/mouse1)
(II) No input driver/identifier specified (ignoring)
(II) config/udev: Adding input device Macintosh mouse button emulation (/dev/input/event3)
(**) Macintosh mouse button emulation: Applying InputClass "evdev pointer catchall"
(**) Macintosh mouse button emulation: always reports core events
(**) Macintosh mouse button emulation: Device: "/dev/input/event3"
(II) Macintosh mouse button emulation: Found 3 mouse buttons
(II) Macintosh mouse button emulation: Found relative axes
(II) Macintosh mouse button emulation: Found x and y relative axes
(II) Macintosh mouse button emulation: Configuring as mouse
(**) Macintosh mouse button emulation: YAxisMapping: buttons 4 and 5
(**) Macintosh mouse button emulation: EmulateWheelButton: 4, EmulateWheelInertia: 10, EmulateWheelTimeout: 200
(II) XINPUT: Adding extended input device "Macintosh mouse button emulation" (type: MOUSE)
(II) Macintosh mouse button emulation: initialized for relative axes.
(II) config/udev: Adding input device Macintosh mouse button emulation (/dev/input/mouse0)
(II) No input driver/identifier specified (ignoring)
(II) Open ACPI successful (/var/run/acpid.socket)
(II) Aug 25 12:11:09 NVIDIA(0): Setting mode "nvidia-auto-select"
(II) Aug 25 12:11:10 NVIDIA(0): ACPI display change hotkey events enabled: the X server is new
(II) Aug 25 12:11:10 NVIDIA(0):     enough to receive ACPI hotkey events.
(II) Aug 25 12:11:10 NVIDIA(0): ACPI brightness change hotkey events enabled.
(II) Power Button: Device reopened after 1 attempts.
(II) Video Bus: Device reopened after 1 attempts.
(II) Sleep Button: Device reopened after 1 attempts.
(II) Video WebCam: Device reopened after 1 attempts.
(II) AT Translated Set 2 keyboard: Device reopened after 1 attempts.
(II) ImPS/2 Generic Wheel Mouse: Device reopened after 1 attempts.
(II) Macintosh mouse button emulation: Device reopened after 1 attempts.
(WW) Aug 25 12:20:23 NVIDIA(0): WAIT (2, 6, 0x8000, 0x00004b44, 0x00005284)
[mi] EQ overflowing. The server is probably stuck in an infinite loop.

Backtrace:
0: /usr/bin/X (xorg_backtrace+0x28) [0x46a798]
1: /usr/bin/X (mieqEnqueue+0x1f4) [0x460024]
2: /usr/bin/X (xf86PostMotionEventP+0xc4) [0x482bf4]
3: /usr/lib/xorg/modules/input/evdev_drv.so (0x7f1c3b77a000+0x53cf) [0x7f1c3b77f3cf]
4: /usr/bin/X (0x400000+0x782e7) [0x4782e7]
5: /usr/bin/X (0x400000+0x125fe3) [0x525fe3]
6: /lib/libpthread.so.0 (0x7f1c41965000+0xf8f0) [0x7f1c419748f0]
7: /usr/lib/xorg/extra-modules/nvidia_drv.so (0x7f1c3c296000+0x68d60) [0x7f1c3c2fed60]
8: /usr/lib/xorg/extra-modules/nvidia_drv.so (0x7f1c3c296000+0x69999) [0x7f1c3c2ff999]
9: /usr/lib/xorg/extra-modules/nvidia_drv.so (0x7f1c3c296000+0xc44b6) [0x7f1c3c35a4b6]
10: /usr/lib/xorg/extra-modules/nvidia_drv.so (0x7f1c3c296000+0x91f82) [0x7f1c3c327f82]
11: /usr/lib/xorg/extra-modules/nvidia_drv.so (0x7f1c3c296000+0x2ff83d) [0x7f1c3c59583d]
12: /usr/bin/X (0x400000+0x134184) [0x534184]
13: /usr/bin/X (0x400000+0xb6cd0) [0x4b6cd0]
14: /usr/bin/X (BlockHandler+0x50) [0x4577f0]
15: /usr/bin/X (WaitForSomething+0x141) [0x469e01]
16: /usr/bin/X (0x400000+0x33942) [0x433942]
17: /usr/bin/X (0x400000+0x261aa) [0x4261aa]
18: /lib/libc.so.6 (__libc_start_main+0xfd) [0x7f1c4065cc4d]
19: /usr/bin/X (0x400000+0x25d59) [0x425d59]
(WW) Aug 25 12:20:30 NVIDIA(0): WAIT (1, 6, 0x8000, 0x00004b44, 0x00005284)
(II) Power Button: Close
(II) UnloadModule: "evdev"
(II) Video Bus: Close
(II) UnloadModule: "evdev"
(II) Sleep Button: Close
(II) UnloadModule: "evdev"
(II) Video WebCam: Close
(II) UnloadModule: "evdev"
(II) AT Translated Set 2 keyboard: Close
(II) UnloadModule: "evdev"
(II) ImPS/2 Generic Wheel Mouse: Close
(II) UnloadModule: "evdev"
(II) Macintosh mouse button emulation: Close
(II) UnloadModule: "evdev"
 ddxSigGiveUp: Closing log