Linux 3.11.10-17-desktop
openSUSE 13.1 (Bottle) (x86_64)
KDE 4.11.5
nouveau 11,403,901 NVIDIA Corporation ION VGA

System hangs randomly, first 30 seconds only bluetooth mouse works, then it also stops. USB keyboard does not work. Hard reboot is only solution.

What may be the problem and how to diagnose?