Cod 6 not responding when started.

Hello,

When i start cod 6 the little square window of cod appears like normal. Then it goes black and its not responding?? I start the task manager and have to end the program. I play cod on 1920-1080 res and best graphics due too a really good pc. Got the nvidea 275gtx ......
+ ive been palying for over half a year and the problem just came like that?

Any help much appreciated