My Sapphire 7950 OC edition did the exact same thing when I first got it. Took out my 5850, put in the 7950 and couldnt get anything on the displays. Rechecked the 6 pin connectors and they were fine. Reseated the card and still couldnt get anything. I put my 5850 in to narrow it down to see if I had somehow damaged the motherboard or if it was truly the video card and my 5850 came right on. I was about to RMA the 7950 but I figured I'd give it one more try. Put it in and it immediately came on. Not sure what the issue was with the first few tries. I'd recommend just reseating the card a few times and be sure to use the right PCI-e slot.