UPDATE:

Gutsy Beta Live CD.
Card is ATI IGP 340M

"lspci -nvv" about my card:

01:05.0 0300: 1002:4337 (prog-if 00 [VGA])
        Subsystem: 103c:002a
        Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping+ SERR- FastB2B+
        Status: Cap+ 66MHz+ UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR-
        Latency: 66 (2000ns min), Cache Line Size: 32 bytes
        Interrupt: pin A routed to IRQ 10
        Region 0: Memory at d8000000 (32-bit, prefetchable) [size=128M]
        Region 1: I/O ports at 9000 [size=256]
        Region 2: Memory at d0300000 (32-bit, non-prefetchable) [size=64K]
        [virtual] Expansion ROM at d0320000 [disabled] [size=128K]
        Capabilities: <access denied>

I checked in /usr/bin/compiz but 1002:4337 is not blacklisted.

I tried:
SKIP_CHECKS=yes compiz
in terminal
and this is the output:

Checking for Xgl: not present.
Detected PCI ID for VGA: 01:05.0 0300: 1002:4337 (prog-if 00 [VGA])
Checking for texture_from_pixmap: present.
Checking for non power of two support: present.
Checking for Composite extension: present.
Comparing resolution (1400x1050) to maximum 3D texture size (2048): Passed.
Checking for nVidia: not present.
Checking for FBConfig: present.
Checking for Xgl: not present.
Starting gtk-window-decorator
/usr/bin/compiz.real (core) - Fatal: No GLXFBConfig for default depth, this isn't going to work.
/usr/bin/compiz.real (core) - Error: Failed to manage screen: 0
/usr/bin/compiz.real (core) - Fatal: No manageable screens found on display :0.0

All worked with Feisty and Open Source driver.

My xorg.conf

Section "Files"
EndSection

Section "InputDevice"
 Identifier "Generic Keyboard"
 Driver "kbd"
 Option "CoreKeyboard"
 Option "XkbRules" "xorg"
 Option "XkbModel" "pc105"
 Option "XkbLayout" "it"
EndSection

Section "InputDevice"
 Identifier "Configured Mouse"
 Driver "mouse"
 Option "CorePointer"
 Option "Device" "/dev/input/mice"
 Option "Protocol" "ImPS/2"
 Option "ZAxisMapping" "4 5"
 Option "Emulate3Buttons" "true"
EndSection

Section "InputDevice"
 Identifier "Synaptics Touchpad"
 Driver "synaptics"
 Option "SendCoreEvents" "true"
 Option "Device" "/dev/psaux"
 Option "Protocol" "auto-dev"
 Option "HorizScrollDelta" "0"
EndSection

Section "InputDevice"
 Driver "wacom"
 Identifier "stylus"
 Option "Device" "/dev/input/wacom"
 Option "Type" "stylus"
 Option "ForceDevice" "ISDV4" # Tablet PC ONLY
EndSection

Section "InputDevice"
 Driver "wacom"
 Identifier "eraser"
 Option "Device" "/dev/input/wacom"
 Option "Type" "eraser"
 Option "ForceDevice" "ISDV4" # Tablet PC ONLY
EndSection

Section "InputDevice"
 Driver "wacom"
 Identifier "cursor"
 Option "Device" "/dev/input/wacom"
 Option "Type" "cursor"
 Option "ForceDevice" "ISDV4" # Tablet PC ONLY
EndSection

Section "Device"
 Identifier "ATI Technologies Inc Radeon IGP 330M/340M/350M"
 Driver "ati"
 BusID "PCI:1:5:0"
EndSection

Section "Monitor"
 Identifier "Monitor Generico"
 Option "DPMS"
EndSection

Section "Screen"
 Identifier "Default Screen"
 Device "ATI Technologies Inc Radeon IGP 330M/340M/350M"
 Monitor "Monitor Generico"
 DefaultDepth 24
 SubSection "Display"
  Modes "1400x1050"
 EndSubSection
EndSection

Section "ServerLayout"
 Identifier "Default Layout"
 Screen "Default Screen"
 InputDevice "Generic Keyboard"
 InputDevice "Configured Mouse"

# Uncomment if you have a wacom tablet
# InputDevice "stylus" "SendCoreEvents"
# InputDevice "cursor" "SendCoreEvents"
# InputDevice "eraser" "SendCoreEvents"
 InputDevice "Synaptics Touchpad"
EndSection