280GTX WON'T START/POST

I have tried two different brands of 280GTXs, EVGA and now MSI. My system will not start with in a single 280GTX GPU or SLI. The case power light blinks and the fans move about an eighth of an inch. If I have one or both 280GTXs installed, my system won't start untill I install my old 8800 in the remaining 3rd PCIE slot. If I install one of my 8800 cards in the vacant PCIE slot with or without the two 280GTXs installed, she boots right up! I've updated the bios. My 1200w Power supply is good. I have to start my system with an old video card in the extra PCIE slot, I remove the 8800 card as I boot up and game fine on my 2 280GTXs. Sure could use some help with this one. All connections are good. All power connections are hooked up. 8 pin and 6 pin are right out ofF the power supply to the video cards.


Any ideas?

System:

ASUS STRIKER EXTREME (First generation nForce 680i SLI chipset , not the Extreme II)
Intel Core DUO 6850
2 MSI 280GTXs (A geforce 8800gtx installed to get system to start)
Corsair DDR2
COOLMAX cuq-1200b 1200w PSU
Blah blah blah ....