GA-Z77-D3H not detecting Sapphire Radeon 7850

I asked this question in the graphics section but I got no response. I'm not sure whether it's a motherboard or graphics card issue.

I have a Sapphire Radeon 7850 which the GA-Z77-D3H motherboard won't recognize at all. It doesn't show up in the device manager and when I install the ATI drivers it installs 'with errors' and I have tried setting the BIOS to use PEG so it picks up the graphics card but that doesn't work either. Basically the card does not exist. Funny thing is my mate has the exact same board and has the exact same problem when I tried the card in his computer.

To check if the PCI-E slot was the issue I tested a Sapphire 6950 which worked fine in his computer but for some reason had a few issues with mine. When I booted the computer a red light turned on on the back of the 6950 and it wouldn't work. I wiggled it around a bit and the light turned off, I reset my computer and then the card worked fine. The 6950 draws more power than the 7850 so it can't be the power supplies that are the issue.

I thought then maybe that the 7850 was the problem but it works perfectly in my old system running an ASUS P6T-SE mother board.

It seems to me that the GA-Z77-D3H has an issue with the 7850. I don't have any other graphics cards to test.

Any help would be greatly appreciated.