Loosing Screen Resulotion

Hi I have a problem that when ever I load a game my computer switches between having a resolution of 1440x900, and not supported. It continues flickering between the two different settings. I have checked all my drivers they are up to date. I have not installed any new software. Last time I used my pc on the 5/12/13 it worked fine when I tried to play any game on the 8/12/13 I have been having this problem.

Any Suggestions would be helpful.

Thanks

Cariosus