Comment 84 for bug 774978

Jadi, Christian, Retrokid, Jules,
   Are you sure it's the same bug? Only a few random X crashes fit into this bug, It's only the same bug if the backtrace (in /var/log/Xorg.0.log.old after X restarts) ends in something like:

[ 15223.014] 2: /lib/x86_64-linux-gnu/libpthread.so.0 (0x7f8335203000+0xfc60) [0x7f8335212c60]
[ 15223.014] 3: /usr/lib/xorg/modules/extensions/librecord.so (0x7f8332bb8000+0x2920) [0x7f8332bba920]

in the backtrace (not the librecord, normally with libpthread near to it).

If your backtrace doesn't include that, or if you're not sure please install the xdiagnose package and then just file a separate bug by running in a terminal:

ubuntu-bug xorg

when you log back in after an X crash.

If you are seeing those in the backtrace then please include your /var/log/Xorg.0.log.old showing the problem on this report.