HD 5850 Upgrade Problems.

AMD Phenon 9850 Quad Core Black Addtion 2.5 GHz
OCZ Platnum DDR2 1066/800 @800
Mother Board: [Gigabyte url=http://www.gigabyte.com/products/product-page.aspx?pid=...][/url GA- MA790X DS4]
Nvidia GTX 285
Corsair 750 Watt PS
1 Sata Drive 1 IDE Drive 1 DVD Drive.

I purchased 2x XFX HD5850 to run in crossfire. At first I had issues getting the system to post because the ram would not seat correctly even though it appeared to be completely seated. -- Fluke? Ram Issue? Motherboard issue?

After swapping the ram around the only way I got the system to post was with ram in slots 1 & 4.

In windows after uninstalling my Nvidia driver I restarted the system, and upon re-entering windows the system randomly restarted. After I got the ATI drivers going I attempt to run Final Fantasy 14, which ends at the character screen restarting the computer. I thought it was a fluke at first, but then I attempted ARMA II, and Left for Dead, all resulting with the sytem restarting. The games all played very very well while I was in.

So, thinking the issue I have could be Power Supply related, I took out one of the graphics cards. I started up Left for Dead and the same thing happened again.

So then I removed the the RAM and attempted to place them in Slots 1 & 3, as prior to the upgrade that is where the ram was and was stable. After the system failed to post I swapped the ram back to 1 & 4 which worked prior, and the system failed to post again, this time, it's as though there is no power at all. The fans twich a little bit... but that is it. No Smoke, No Smell, Just nothing but a few twitching fans.

Any help in this matter would be greatly appreciated.