Single repeating beep NF7 Rev 1.2

[bigcarp]

My faithful NF7-S Rev 1.2 rig is giving me fits. The power supply died so I bought a new Antec Earthwatts 500w to replace it with. After installing the new P/S I get the single repeating beep tone. I can't tell if its the short or long beep tone. The beep lasts approximately one secod with a pause between beeps. Thinking it was the long beep tone(DRAM related) I reseated the RAM, tried a single stick is all 3 slots, cleared the CMOS, and even tried another stick of RAM for a second working system. Still the beep. I have a spare Rev2 mobo which I installed and I get single beep with this board as well. Thinking the P/S might be bad I exchanged it for another of the same model, that didn't work either. Should I try another brand/model of power supply?
Any other ideas or suggestions appreciated.