The video card section is where you should post this....
and also, you gotta give us your system specs, cause it matters as to tracing the problem.
First, are your drivers and BIOS updated, card and mobo?
Second, is the fan clean from dust buildup and spinning? and does your case have good cooling/airflow, since it could be overheating.
Third, Run DXdiag's test and see if any problems there.
Are you overclocking?
What are your voltages and temps?
Where you holding a religious amulet and raising right hand while balancing on one foot chanting "Hail to the King, Long live Bill Gates!" with 64 candles lit in a shrine around the PC?
We just have to know these things to help any further, along with your personal information and banking routing numbers.