Originally Posted by johnnyNZ

i had the exact same problem with my new build, thougth it was my psu so upgraded from a 400W to a new silerstone 560W still didn't resolve the problem - the computer would still not P.O.S.T. tried another graphic card, cpu, and HD so ended up taking it back to the shop where i brought the parts and they couldn't resolve the problem either so now i'm waiting on a new motherboard and cpu, hopefully that will fix the problem.
i'd say your mb is faulty.

Gigabyte GA-N650SLI-DS4L Motherboard
E6750 2.66 CPU
XFX 8800GT xxx edition
2 1GB 800 ram
320GB westerndigital HD