https://bugs.freedesktop.org/show_bug.cgi?id=39897

--- Comment #18 from Alex Deucher agd5f@yahoo.com 2011-09-25 10:42:18 PDT --- Does:

Option "ColorTiling" "false"

in the device section of your xorg.conf help? If so, you may have an old version of the 32 bit 3D driver which doesn't handle tiling properly.