Created attachment 102697 [details]
Xorg.0.log

I did a little torture testing with a fully updated Debian sid. This one
happened (I think) playing some random video from my disk with VLC but it might
also have been been caused by iceweasel with a couple of large images open.

xserver-xorg-core 2:1.15.99.904-1
libgl1-mesa-dri 10.2.3-1
vlc 2.1.4-1+b3
iceweasel 30.0-2

Sorry no symbols, I just installed them - will try to reproduce it with
symbols.