ASUS P6T Problem---- HELP!

Built a new system with these specs:
Intel i7 920
Asus P6T
6 gigs Corsair triple memory 1600
BFG 9800 GT 512 meg PCI-e
WD 640 gig hard drive
DVD/CD combo drive
Antec 300 case
BFG LS-550 power supply

All works well until I turn off the system and my surge protector. When I turn it back on, all of the system settings like date and time are all changed to default and have to be reset every time. As long as the power is plugged into an outlet, it keeps the info. Unplug and it is reset.

I have changed the CMOS battery and cleared the CMOS numerous times. I replaced the motherboard four times, once through Asus because they tested a board personally for me and said it worked. I recieved it and same thing happened. I replaced the power supply twice, the i7 920 twice, the memory twice, still same problem.

I built the system out of the case with just the CPU, memory and video card, same issue. I was told to try another power supply. I tried a Antec 650 earthwatts and it worked for 30 days, then same issue. Just bought a Corsair HX620, same issue.

I don't get why the Antec 650 worked for a while but nothing else does. Everyone is baffled and nobody can help me.

All of the power supplies work in my other computers just fine so I don't think that is the issue. Any guidance would be greatly appreciated!!