Comment 128 for bug 973096

I downgraded to NVIDIA 275.43 and the problem is gone, so it appears to be a problem with recent Nvidia drivers.
I don't know of a good way to downgrade though, I just removed nvidia-current and nvidia-current-updates, blacklisted nouveau module as well as plucked it from initramfs and installed the 275.43 nvidia drivers from nvidias homepage. Obviously that kind of hack won't survive a kernel upgrade, I just did it to check if an older nvidia driver would indeed alleviate the troubles.