This happens most often when the mobo detects bad timings in the bios which it considers an "overclocking failed" situation. Usually clearing the CMOS resets everything to default and lets you boots.
Has the computer ever POSTed? Or have you never been able to get into bios?
If so have you changed RAM timings?
Have you tried booting with a single stick of RAM?
Have you tried clearing CMOS by pressing the switch at the back of the board, under the LAN port?
Just trying to figure out which steps you have / have not taken in order to determine the best course for troubleshooting.
EDIT: Try swithing out your GPU for another one or switching it to the 2nd slot before clearing CMOS. I personally could not reset CMOS and get the mobo to POST if I kept my HD 5850 in the first PCIE. However, if I put an HD 3870 in it, I could clear it and get the computer to POST. Then I could switch out my HD 5850 back in and the computer would run...weird and stupid...I know...these boards are finicky and terribly uncompatible.