https://bugs.freedesktop.org/show_bug.cgi?id=61182
--- Comment #9 from Alex Deucher agd5f@yahoo.com --- (In reply to comment #8)
I don't have a usable backtrace at hand, but I'm seeing very similar crashes in gnome-shell as well with Mesa 9.1 and Linux 3.8.3. With Mesa 9.0.3, I haven't noticed any crashes so far. It crashes much more frequently with two monitors (both 1920x1200) attached than with just one.
Can you bisect mesa?