Not Optimum mode Monitor problem

[demo]

Hey guys, I just downloaded Ace of Spades today and was really looking forward to playing except i have a problem. Every time i play the game a box pops up saying my monitor is not using the optimum mode of 1920x1080. When this happens it automatically minimises me from the game. It is happening so frequently i have not yet been able to play. Any tips on how to fix this would be much appreciated. My monitor is a Samsung Syncmaster 2233sw.

Regards demo