Created attachment 69702 [details]
kernel messages of the crash

When opening http://lwn.net/Articles/522127/ with firefox16 the screen goes
black for a moment and then reappears for a few seconds after which it goes
black again. This cycle goes on a few times after which the system completely
locks up (even Magic Sysrq seems to have no effect).

I don't know if it is related but sometimes opening huge images in firefox
causes X to crash, too. This, however, doesn't freeze the kernel and beside the
crash itself everything works normally afterwards.

kernel: 3.6.6
xorg-server: 1.13.0
xf86-video-ati: 7.0.0
mesa: 9.0