I have a frequent xserver crashes when trying to switch users (either via GDM or CTRL-ALT-F7...).
Backtrace from Xorg.0.log.old alvasy ends up with:
0: /usr/bin/X(xorg_backtrace+0x3b) [0x8133d6b]
1: /usr/bin/X(xf86SigHandler+0x55) [0x80c7d35]
3: /usr/bin/X [0x80f99f0]
4: /usr/lib/xorg/modules/drivers//nvidia_drv.so [0xb5eb55f7]
Saw signal 11. Server aborting.
It happens with default 185.18 drivers, and also with 190.53.
Filed a bug on the launchpad, but for now no response:
I need help in finding out if this bug is nvidia driver related or not and how to trace the issues from here.