Check then recheck all your power connections going to the motherboard. It sounds like one of them might be improperly seated. Make sure the 4 pin (or 8 depending on your MB) power for the CPU is properly connected.
Try clearing CMOS. (read your manual for instructions on how to do this)
If that doesn't work, check then re-check that the memory is properly seated. If it still doesn't work then try re-seating the expansion cards. Try booting with only the video card in the expansion slots. Try moving the video to different PCI-E slots (if you have multiple). Try using only one memory stick. Try moving the memory to different slots. Try using a different memory stick.
Finally, if all that still doesn't work, pull the CPU out. Inspect the CPU for dust/debris. Inspect the CPU socket for dust/debris and bent/broken pins.
For initial boot you really want as little a possible attached to the motherboard, especially in a situation like this. This mean no USB extensions, no hard drives, no CD-ROM, no audio expansion card, etc. etc. etc. All you should really need to get into BIOS for the first time is a power supply, graphics card, ONE memory stick, CPU, and keyboard. And a monitor (of course).
If all of this fails to correct the issue then it is possible you may need to RMA the board. I've had to RMA a board straight out of the box for a similar issue. Only difference is mine would 'blink' during boot, which would really piss the graphics card off and make it scream bloody murder until I shut off the power.
The point is that you want to exhaust every possible option before sending the board back. Often when you RMA a board to the factory it is their policy to send you a refurbished replacment, and I'v gotten a couple of really crappy refurb products this way. It would also really suck to get another board to only have the exact same problem... meaning the original board was probably perfectly fine.