Happens to me also, and I can reproduce it if I connect a second monitor.
First monitor turns off and the second turns on.
If I enable the second monitor from system settings, X crashes every tie.
Bugreport: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1541932
Happens to me also, and I can reproduce it if I connect a second monitor.
First monitor turns off and the second turns on.
If I enable the second monitor from system settings, X crashes every tie.
Bugreport: https:/ /bugs.launchpad .net/ubuntu/ +source/ linux/+ bug/1541932