Created attachment 71998 [details]
syslog

The bug was introduced in drm-next between 12/06 and 12/11 according to
ubuntu's kernel builds here:
http://kernel.ubuntu.com/~kernel-ppa/mainline/drm-next/2012-12-11-raring/

Error messages from syslog attached.

01:00.0 VGA compatible controller: Advanced Micro Devices [AMD] nee ATI RV670
[Radeon HD 3870]

I am using Xorg-Edgers mesa/Xorg, but the crash also appears when I go back to
stable mesa/Xorg.