I just recently picked up a Sapphire HD 7950 Vapor-X, installed it, and was pleased to see it running perfectly. However, when it came to OCing the card, it just wouldn't deliver.... at all. First, I tried 1100/1575 on stock voltage using TRIXX. I ran Heaven and 3DMark, each time having them both freeze my PC halfway through. Now, seeing as how voltage may have been a problem, I used Afterburner and boosted it to 1.25mw, and still, every time, my PC would crash halfway through the benchmarks.
At this point I started to experiment to try and source out the problem. I ran both Heaven and 3DMark at their lowest possible settings, with the card still OCed. Still the same results, leading me to believe that the problem may be in the actual card. Even marginally overclocking the card would produce the same results. I should also add that when OCed, the card only reaches 36 C max. Usually lower.
However, when I completely reset the setting back to factory stock, everything ran perfectly. This really has been a letdown seeing as how I researched the amazing results this card can produce when OCed.
Oh and also, drivers are all updated.
EDIT: Card currently has "Boost" enabled, which is pretty much Sapphire's factory OC stuffed into a second BIOS, so the card is running 950/1250
Corsair Vengeance 8GB DDR3
750W Corsair PSU
1TB WD Black