No post no beep no video (by 2 users)

I recently purchased a new motherboard and processor because my old processor overheated. I installed CPU, memory, and video card and i get all the fans and lights on but no beep codes or POST when the system is running. There is no video, although the screen does flicker when i turn the power switch on. In short, all fans + lights on, no POST or beep codes. I RMA'd this motherboard because i thought it was the problem but am getting the same problem with the new motherboard

Intel Core 2 Duo E6600 Conroe 2.4GHz LGA 775
MSI P6N SLI Platinum LGA 775 NVIDIA nForce 650i SLI ATX Intel Motherboard
EVGA 256-P2-N615-TX GeForce 7600GT 256MB 128-bit GDDR3 PCI Express x16 SLI Supported Video Card
650 watt power supply