If it's just the PWR LED flashing, then it's a psu issue. Same thing happend to my rig (sig) except all i did was use air to get the dust bunnies out. Next thing all i get was the flashing of the PWR LED on the mobo. I thought the mobo was dead, switched out psu's and the mobo is fine.
If you have another psu swap it out and see. Keep me posted-