Try re-seating all the board power connections, and make sure you're either using the 24 pin connector, or 20 + 4 for the cpu.
I agree on this one, because it sounds like it is time to look at a RMA. Enermax has always been a very solid and strong supply as Doby mentioned. However, if you read some of the recent reviews in the past six months, ,they are having some great difficulties with DOA and short term failures in their supplies for some odd reason.In any event I would rma it, with the system working with the old psu suggests this one is bad, sorry and enermax usually makes very good psu's