Comment 9 for bug 158761

Bram, your backtrace also does not match up to Ryan's so is likely an unrelated bug. Please report it separately. It would be great if you could get a 'full backtrace'. You can ssh into the box when it has crashed from another system and attach gdb to Xorg to get it. (see https://wiki.ubuntu.com/DebuggingXorg for directions)