run a dxdiag and post up the result in a txt file please this way we can sort throu and have a look and yes a screen shot of the problem will help track it down aswell. But for the moment try disabeling post proccesing and maximising your memory allocation in troubleshooting in the video tab.
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Also knowing your GFX card and / or other system specs you may be able to provide will help the DEV's track down your issue.