voltage phenomena?

im having a bit of trouble getting my 7950 stable. im still not sure what to use to check stability since i can run kombustor for like 10 min and run 3dmark11 a few times in a row and then 40 seconds into metro 2033 and it crashes. but the thing thats making it more difficult is the fact that at high voltages the card seems to be unstable regardless of the clocks. for example, at 900/1250 and 1300mV it crashes. yet at 1090mV its fine (of course). then i can try 1195/1405 at 1200mV and it will run for a while.. but at 1300mV it dies. the card isnt overheating either.. im frustrated because i dont understand how it can be unstable based on the voltage alone when the temps are fine.

sorry to bump, but no one has any thoughts on this? im just finding it strange that it would be unstable on stock clocks with a high voltage and low temp. my only idea would be perhaps the psu? but i used to have two 5870s in crossfire and it was fine power wise. i cant see how a single 7950 would use more power than those two.