I bought a GTX 660 approximately 2 and 1/2 months ago, and have had little to no problems with it until yesterday (2/8/13). It started when my display went blank during a game. After I restarted my graphics drivers starting crashing and discolored clumps of pixels started popping up. I rolled back my drivers which made my screen go blank again, and also made me unable to boot Windows as it would go blank at the welcome screen. So I booted in safe mode, ran system restore and installed a legacy driver which seems to have fixed the boot problem for now.
Now, I am unable to boot Windows with any Nvidia driver newer than V. 305.27. The display simply goes blank after the "Windows starting" animation. Additionally, attempting to launch any Steam game results in either the game crashing within 20 seconds or the display going blank & monitor indicating a loss of signal. I'm assuming this is related to Directx but I can't say for sure.