CrossfireX Problems / Motherboard or Cards?

Alright, Im assuming Im missing something rather simple here so I'll make it concise.

I recently bought another 5770 in hopes to crossfire them, but Im having a lot of trouble getting this to work. My motherboard has two pci-e slots on it. One is listed as a pci-e x16 (PCIEX16) and the other is listed as pci-e x16 (PCIEX8). Now the problem lies in that whichever card is placed in the latter slot is not detected by windows device manager or CatalystCC. Both cards run beautifully in when placed in the (PCIEX16) slot so I know its not the card, and I have ample power running to each of the cards.
I thought it might be a faulty pci-e slot, but when I leave out a 6pin the motherboard beeps a warning and both cards power up and have their fans spin when everything is connected.

There's a couple things that threw me for a loop. HWmonitor, a hardware monitoring program I have, detects when both cards are seated even though windows device manager does not. I also tried booting with just a single card placed in the second slot and windows device manager detected <NO> display adapter whatsoever, and same with CCC.

Now this is really starting to bug me. Am i missing something really simple here? Bios options for pci-e slots are limited to which to use as the primary slot so Im out of ideas here.

Any help is greatly appreciated.

Motherboard: GA790xta-ud4
CPU: AMD x4 965
GPU: 2x xfx 5770
PSU: 700w OCZ modxstream
RAM: 2x 2gb ripjaws ddr3 1600
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  1. Just checking back in, If buying a new mobo with two pcie x16 (PCIEX16) slots will resolve this please let me know. Would rather end this with a simple purchase then tinker around for who knows how long.
  2. The fact that your slots are X16 and X8 should not be causing any sort of a problem. Start with easiest and move to hardest. First, uninstall your ATI drivers in the control panel. Then enter safe mode and use the program called driver sweeper to remove all ATI drivers. Then reboot into Windows and reinstall the latest ATI drivers...
    If nothing is detected, reinstall your operating system doing a clean install of Windows. Then install ATI drivers. If nothing still works...then it's probably a faulty motherboard or a motherboard that doesn't like those cards. In which case I'd buy a new motherboard. Check online for reviews to make sure its a motherboard that gets praise for working well with Crossfire. You may think that reinstalling the OS (my step 2) is a unnecessary headache if you can resolve your problems buying a different motherboard, but if you install a new MB you'll have to reinstall your OS anyway. Might as well give it a shot if Step 1 fails if it can save you some money,
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