I'm sure this has already been done, but to double check, make sure that you are not running any other programs that use DirectX; this problem (Frequently) occurs when a third party program makes use of directx. I experience it most often with Netflix (which uses Silverlight). The problem can also be caused by Internet Explorer 9 (which has some acceleration features that may be enabled) and Firefox 4. This problem can also be caused by DirectX not being properly released by another program after its been closed, so double check your running software after a clean re-boot.