I'm having the same problem. I changed to different resolutions and messed with the 2 monitors in the display settings box, and I'm still having the same issue. Please help.
If it is a laptop you are using just hit the function key (Fn) on the bottom of your keyboard along with F7. Some computers have a different assignment, such as F8 but it will be the one with a blank display and a filled in display on it. Just push on that several times until you get the configuration you want.