Black Screen HELP !

Hello guys, i have purchased a new graphics card Asus Hd6850 v2 but i have problem with it its not that often but i get the Black Screen or White Screen at least 2 times a day. It always happens when im watching film at Windows media Player or on youtube i dont know why its something BSOD but only the black screen or white screen appears. When i get white screen after few seconds its changes to black and i have to reboot a computer. THis thing happens only when im watching something but when im playing games like Battlefield Bad Company 2 or Battlefield 3 it never happenes. Im really confused about that im thinking to reclaim this GPU if anyone can help me please just post the answer.


My computer specs:

Mobo: Asus P5Q-VM DO
CPU: Intel Core 2 Quad Core Q6600
PSU: Coolermaster 500W Extreme
RAM: OCZ 4GB

THank You