Well, someone had to do it...

By the way, the issue was truly horrendous FPS stutter. Looks like microstutter, except that's a multi-GPU specific issue. Anyways, near as I can tell, there's no fix. I ended up wiping my system. However, it does seem to be tied to a specific file (Likely a driver) so you can do a system restore with little fear. An easy way to tell if it's the same issue I had (At least on Windows 7) is if you mouse over your desktop icons and when they do the background-fade-in thingy, they will stutter and hang up if you mouse over them fast enough.

Well, I certainly missed having you around. Glad to hear your computer's working again!