Comment 7 for bug 748137

I wouldn't normally opine into something like this, but on the off-chance that it could be a possible cause:

Graphics Card: 01:05.0 VGA compatible controller: ATI Technologies Inc M880G [Mobility Radeon HD 4200]
Computer: Compaq Presario CQ62
OS: Ubuntu 11.04 Beta 1 x86_64

I installed the FGLRX driver earlier today, and found it generally has issues with more or less everything OpenGL, proceeded to remove it, looked a bit into modprobe.d, and commented/removed two lines (one or both of which I may have added myself when I first installed 10.10):
/etc/modprobe.d/blacklist.conf: "blacklist fglrx"
/etc/modprobe.d/blacklist-framebuffer.conf: "blacklist radeonfb"

I likewise modified xorg.conf to use fglrx, though this may have been unnecessary:
Section "Screen"
        Identifier "Default Screen"
        DefaultDepth 24
EndSection

Section "Module"
        Load "glx"
EndSection

Section "Device"
        Identifier "Default Device"
        Driver "fglrx"
EndSection

At any rate, its just a possible cause; I had also prior to the installation of FGLRX had xorg-edgers installed (apt purged it before doing any of this, though), and the machine itself was an upgrade over 10.10. Likewise, I have yet to be able to run Unity for whatever reason [well, actually, the 11.04 upgrade screwed up the /usr/bin/xsessions directory for some reason; prefer KDE anyway].