Problems with screen resolution

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http://askubuntu.com – Ok... So I am running Ubuntu 12.10. I installed a NES emulator from the software center. I downloaded a ROM, played it, and everything worked fine. I decided to run in full screen mode (Because it's not fun playing on a 2-inch screen) and it properly switched resolution to 640*480 to run in full screen mode. Then, being used to windows, I used Alt+Enter to Exit full screen mode. The program closed and I was at my desktop, but it was in 640*480 still. I went to System Settings, Display, and changed to the proper resolution. When I clicked apply, though, the screen went black, and acted like the (HowTos)