I use Gentoo, and the the gui (KDE) sometimes locks up for a few secs, and the computer (xorg) freezes daily. I can ssh into the box, so I made an nvidia bug report:
I haven't experienced this with nvidia driver version 275.43
or lower. XOrg downgrade in itself didn't helped. The Powermizer set to max performance helped maybe, but lock-ups and computer freezes remained. I haven't enabled mtrr sanitizer, but there aren't any uncached regions also.
Card is: NVidia GeForce 8400M G
Edit: Switching to nouveau driver works for me.
(Maybe it is not so fast, and doesn't support OpenCL, but for now an X without lock ups and without freeze is OK.)