Input not supported

hi , i have recently been playing modern warfare 2 multiplayer (the steam version) and have tried a number of different resolutions to experiment what effect a different res would have on my fps.

however when i selected 1440x576 my screen went blank and input not supported appeared.

the game didn't have a time out screen when i changed the res so i am now stuck with the input not supported message whenever i try to play the game.

i have tried steams launch commands but they dont seem to work at all.

my native res is 1920x1080 and i have a 3870x2 graphics card.

some one please help ! lol