Try changing screen resolution, I know that sux if your used to what you got, but this was the only way I could fix it on mine. And I'm running 2 19' widescreens(1-vga/1-dvi). If anyone has a better solution I'd be interested myself!
This use to happen to me. I restared the game and it worked fine. Ive had it done to me a few times thats all I do but it seems to work great now. Hope this helps ;)