You should definitely clean your pc! But your idle GPU temps are fine (your CPU is as well), so I doubt that's the problem. Any problems detected by Memtest are more likely to cause BSOD-109 errors. Unless one of your dimms came loose and you're now playing with half the RAM you were a few days ago (that's actually happened to me before). The drivers are your best bet- though it would be pretty funny if you had just set your PC to "power saver' mode or something.