Gigabyte EP45 UP3D (rev 1.6) Does Not Detect Second PCI-e Card (HD4890

I had trouble deciding if I should post this under GPU or Mobo, but the GPU works fine and ATI support said it's probably mobo related... so here we go. I've found that whenever I troubleshoot my builds I end up on this site a lot and maybe someone's having the same problem as me and is just waiting for someone to speak up... that's what brought me here.

PC Setup:

64 bit Vista Business
Gigabyte EP45 UD3P (rev 1.6) mobo
Intel Core2 Quad q9550 (not overclocked) @ 2.83ghz
8gb (4x2gb) Kingston Ram
Corsair HX850w PSU
PCI Wireless Adapter
Dual PCI-e Sapphire ATI HD4890s crossfired
1 TB harddrive
Lightscribe DVD-R CD-ROM

I have a really peculiar problem...

My motherboard occasionally (though not often) detects my second HD4890 card. The card in the 16x slot it detects, but not the one in the 8x slot. When I go into device manager it only detects one display card and if I plug my monitor into the other slot it doesn't receive a signal. If I designate my second PCI-e slot as the primary display it still doesn't detect it.

The cards themselves and the individual PCI-e slots work (I've taken the card out and tested each slot individually with each card) but when both are in use they are not detected. I have updated my BIOS, my chipsets, reinstalled Catalyst (took out one card, installed CCC, rebooted to desktop, replaced second card), set it back to factory defaults, swapped the cards, played with my BIOS, tried removing my PCI WAN card, reducing my memory to 4gb, and fiddling with power cords.

I really don't know what to try next. Messing with Catalyst will once in a blue moon fix the problem, but no solution has ever worked for more than day or twice in a row.

Please help! Also, please don't address the fact that I may have CPU bottle necking, I'll cross that bridge when I can get better cooling lol

unrelated. I have kingston gaming RAM that's supposed to run at 2.2v but when i set it that high it gets really hot. what's the lowest i can set them that they'll still be useful? (i heard that if you use all 4 ram slots you need at least 2.0)