Black Box Following Cursor

[Mooecow]

I just booted my computer to find an odd problem. On the left side of the screen, there is a rectangle that follows the mouse up and down. It is either white or black, depending on the position of the cursor. I didn't change any settings or update any drivers before this started occurring. I'm running the latest Nvidia drivers (93.71) and I already tried rolling the drivers back to 91.47 with no luck. The video card is a 7900GTO.

Heres a poor picture of what is happening.
http://img133.imageshack.us/img133/9146/p1010017sv5.jpg

Thanks