This seems to be related to the ppa package "touchpad-indicator" that I installed. After removing this package, this X-segmentation-fault problem disappeared. I found that I can use Fn+F8 to enable/disable touchpad in my Thinkpad X220, and don't need that package anyway.
I think this bug can be closed. ** Changed in: xorg-server (Ubuntu) Status: New => Fix Committed -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/968169 Title: Xorg segmentatoin fault and logs me out To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/xorg-server/+bug/968169/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs