Gainward GTX 275 memoryclock jumping?

Hey Guys,
Need some help here. For the last few weeks I've been having real problems with my card.
Basically everything runs fine and dandy, until I start to play a game.

5 or 10 mintues into the game, my memory clock speed will drop (and be locked until a full reboot) at 250.
I've tried the following:
- Updated drivers from 180 till recent, trying each one on its own
- Underclocked the card
- Overclocked the card

I've posted a picture, so hopefully this might help.



Basic specps run down.

Intel Quad Core q6600
4gb DDR2 ram
3 internal drives
Coolermaster 650W PSU
Windows 7 RC1

So run down on the problem, card memory clock falls from 1134 to 250 when gaming, have to reboot to get it back up.
Best Regards,

Charl Du Plessis