EtherDongle? USB?
are there any other pixel stuff connected? do they act up?
you can't determine the power output on +12v based off the watt rating of the power supply, as it's factoring in the total wattage across all voltages combined. I have 2 types of 600 watt power supplies on hand. One has 24Amps on the single 12v rail. and the other has 16Amps.