So I've been fiddling with these nVidia beta drivers for a while, trying to get SLI working reliably, when I decided to update DirectX. At some point during the installation, my computer locks up. After, that same lock occurs when starting Starcraft 2, and Left 4 Dead 2 crashes without completely locking up my computer. It's concerning, because both these games worked perfectly well, beforehand. I've done everything I can think of to remedy the situation, but I've had no luck. Dragon Age: Origins, Alien Swarm, and others work perfectly fine.
The problem isn't remedied by removing one the GTX 460s in SLI configuration. I reset the BIOS to defaults, uninstalled and reinstalled fresh beta and current nVidia drivers, uninstalled and reinstalled Starcraft 2, installed an old version of DirectX, etc. Right now, I'm running a bunch of test and repair tools before I back everything up and install a clean copy of Windows 7.