Ok, I found this thread that illustrates exactly the problem I'm having:
http://www.evga.com/forums/tm.asp?m=253891
It seems more like a problem with the chipset, either a driver or a hardware bug. This thread turns out to be for the 780i chipset but mine is a 750, but the symptoms are exactly the same. Any suggestions? I posted to the NVidia forums on the off chance that someone can give me a solution, but at this point it might be a case of going to a different board and putting this one on Kijiji... since I'm sure the board itself is not technically defective...