If I alt-tab to get out of the game and then go back in the video display doesn't fill the screen anymore, there is about a 1 inch gap at the bottom of the screen that shows whatever I was last looking at.  I also notice that the cursor will not move to that bottom section, it is trapped inside the rest of the screen which is displaying the game.  My resolution in game is 1920x1080 and checking it after I return to the game it still claims 1920x1080 even though it no-longer fills the entire screen.  However my normal screen resolution is 1920x1200 so maybe this difference is the issue?

Nvidia GTX 550 Ti