I've seen several threads that mention similar problems, but they haven't help fixed the problem. It's driving me nuts as I have to reboot the computer to switch user accounts, as Xorg crashes when logging off, and I have to hit power button on the desktop. I'm using ATI drivers with GDM.
Here is the output from lspci http://paste.pocoo.org/show/542226/
and the Linux Kernel config is http://paste.pocoo.org/show/542227/