Problems with Radeon 4890 and Evga 750i??

[kpolu]

Basically my old video card has been having some problems of late crashing during games so I replaced it with a Radeon 4890. After I installed it I get a series of beeps and they post code of "7F" on this motherboard. So i put the old card back in and it posts fine (the old card is a GTX260 btw). So I figure the new card is bad, but really quick I put the new card in my kids computer and it comes up perfectly fine. So i take the new 4890 to a friend who owns a computer shop and we test the card in 3 different motherboards and it works fine in all 3. So I take the card back home stick it in my computer and still nothing, same beeps and same post error code. I then have that friend bring over his GTX280 and a 4870x2 and they both work perfectly in my computer but again the 4890 does not. Now I really don't think it's a power supply issue as I have a Corair 1000W and every other video card I try in my computer works fine. Yet the 4890 works perfectly in any other computer. I've done a bios update, cleared the cmos, tried the card in the 2nd slot, using the 6pin PCIE power adapters that came with it, basically anything that I could possibly think of and I'm pretty much tearing my hair out at this one. Is it at all possible that the card and motherboard don't like each other? Anyone got any ideas?