Honestly, if you think its the card and not the drivers, motherboard, or something else, I would call eVGA and see if you can get RMA. I have read they have very good tech support.
Its worth a try before buying a new card. If you do buy a new one, you may want to consider a 6800 NU or perhaps a 6600GT when it comes out, depending on how much you want to spend. Hopefully tho eVGA will RMA your card