I just thought I would share something I've known for a bit. The other day I was trying to get a game to run properly (Mirrors Edge in triple-wide) and it seemed like no matter what I did, it ran fine but with shitty FPS. I knew I had run it fine prior but some configs got messed up so I just kinda gave up. Since I wanted to play Mirrors Edge and got nothing but problems, I gave up and settled for a different game: Splinter Cell Conviction. Except, when I loaded the game, the FPS was also terrible. This is an instant clue for me since I've been there and done that; my graphics card crashed. One of the cool things in Vista & 7 is that instead of tossing you a BSOD, Windows can attempt to recover a crashed driver. I don't know why specifically but whenever that happens with an nVidia card and newer drivers, the clocks on the card revert to a safe value (maybe for overclocking crashing?) which is something like 300mhz or 200mhz for the core. A simple restart puts your clocks back to normal but I thought I would share this in case anyone had weird issues ever.
*EDIT*
Depending on what you're doing, you may see an error like this:

Although something was freaking out (probably cuz of the beta driver) and mine kept crashing every 5-15 seconds or so just now and it didn't revert the clocks to the 2D settings. If you ever come across this, check GPU-Z in the Sensors tab and see what your clocks are.