You definitely have a video related problem and one that appears to surround the driver. However, sounds like you are current on the Nvidia drivers (please confirm that you are running the latest from nvidia.com). How are your GPU temperatures at idle and under load?
Are you monitoring the temperatures of your CPU and GPU? Overheating GPUs can cause artifacts and crashes. Use something like CPUID HWMonitor to make sure you don't have heat issues. Also, if you haven't recently, clean the dust out of your case using canned air.
Bur if your temps are fine then I dunno. Does it require a reboot to make it go back to normal?
Yes, and while the GPU can take that temperature, it isn't good to run your GPU at that temperature. You probably have dust clogged in the heatsink fins of the GPU & CPU and also the front intake and back exhaust ports. I suggest a can of duster that is approved for use on electronic equipment. Pay attention to those heatsink fins.
Of course there is no guarantee that will fix your problem, but your GPU will love you for it.