Comment 8 for bug 561538

I have almost the same issue since I installed Lucid Lynx : when I disconnect as a user I get a black screen and the only thing I can do is reboot with Alt+SysRq+B. It happened twice out of two trials.

Here is the tail of my Xorg.0.log.old, I suppose to be related with this issue :

(**) Macintosh mouse button emulation: Applying InputClass "evdev pointer catchall"
(**) Macintosh mouse button emulation: always reports core events
(**) Macintosh mouse button emulation: Device: "/dev/input/event2"
(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) Power Button: Close
(II) UnloadModule: "evdev"
(II) Power Button: Close
(II) UnloadModule: "evdev"
(II) AT Translated Set 2 keyboard: Close
(II) UnloadModule: "evdev"
(II) ImPS/2 Logitech Wheel Mouse: Close
(II) UnloadModule: "evdev"
(II) Macintosh mouse button emulation: Close
(II) UnloadModule: "evdev"
(II) Open ACPI successful (/var/run/acpid.socket)
(II) APM registered successfully
(II) NVIDIA(0): Initialized GART.
(WW) NVIDIA(0): WAIT (2, 6, 0x8000, 0x00000300, 0x000003cc)
(WW) NVIDIA(0): WAIT (1, 6, 0x8000, 0x00000300, 0x000003cc)
(II) NVIDIA(0): Setting mode "nvidia-auto-select"
(WW) NVIDIA(0): WAIT (2, 1, 0x8000, 0x00000300, 0x0000046c)
(WW) NVIDIA(0): WAIT (1, 1, 0x8000, 0x00000300, 0x0000046c)
(WW) NVIDIA(0): WAIT (2, 3, 0x8000, 0x00000300, 0x00000880)
(WW) NVIDIA(0): WAIT (1, 3, 0x8000, 0x00000300, 0x00000880)
(WW) NVIDIA(0): WAIT (2, 11, 0x8000, 0x00000300, 0x000008a0)
(WW) NVIDIA(0): WAIT (1, 11, 0x8000, 0x00000300, 0x000008a0)

As you can see I have a NVidia video card (an old one).
CPU : AMD Barton.