Is this the v2 version (The fixed one)
Also, remember overclocking is the luck of the draw. You might of gotten a terrible overclocking card. I recently purchased the V1 version, and I love it. I've done some heavy overclocking to it, and its been able to push 1.2 GHZ because of its enormous heatsink.
As long as the card is working at stock clocks without crashing, the store probably wouldn't accept a return.