2 things come to mind, either re-install directX or if you are using a Nvidia card try an earlier driver. A few people had problems with the latest Nvidia drivers. (And I also realize many others 'didnt' have problems with the latest nvidia drivers!)
Just thought I would add that bit to stop people writing in that they dont have problems with the latest drivers but it may help in your particular case! I'd try DirectX re-install first tho.
