It seems I'm having some issues with my video card.
At first, I thought it was dead. I was playing Frontlines: Fuel of War, and my PC had a weird graphics glitch, then locked up. I rebooted and was able to play for another hour before it did the same thing. When I rebooted again, Windows showed up in 640x480 and 4bit color. (Pretty much illegible.)
I tried a bunch of trouble shooting, but all signs pointed to the video card being the culprit. So, I ordered a new XFX Geforce 260 card.
Of course, now my video card seems to be OK, so I'm guessing it overheated. Unfortunately, my PC is already well ventilated, and the cooling is pretty much top notch without going to water. My guess is that it's just going to keep happening until I replace the card anyway.
UPDATE: Of course it wasn't working. 2D works, but as soon as I attempt to use ANY 3D program *BAM!* the screen goes all funky and then the PC locks up moments later. And when I reboot after trying a 3D program, even my BIOS screen is all messed up. Doh!
Oh well, my new card should be here tomorrow.