If you have not done so since installing the monitor driver, reinstall Catalyst so it can reset itself to the new monitor driver.
If that does not work I do not really know what to say. I have the same problem in some older games on my 19" 1440x900 Samsung. However, those are relating to the games only supporting 16x9 format resolutions and my monitor being 16x10 format. This should not really apply in your case as yours is 16x9.
If you set the game to your monitors native resolution of 1366 x 768(720p), it should just work. I could not find any info on FIFA 11. All I saw was FIFA 12, but no mention of what resolutions it supports. I do know your video card supports 1366 x 768 and well beyond that.