I've been having a few graphics related problems, which turned out to be an intermittent GPU fan on my Nvidia TI-4200 Gainward card. Its out of warranty and no amount of cleaning would make it the fan reliable.
I was about to give up when found The Coolingshop, Vantec Iceberq 4 Pro VGA Cooling Kit. Its a direct replacement for my fan and heatsink. (Even has a blue light).
Ordered with free delivery and resurrected my TI-4200 within two days!