Prusa Mendel I2 - Turning on extruder heater trips ATX supply

Hi all -
I have built a Prusa Mendel I2 (with Sanguinololu) from a kit, and included is an extruder assembly.
Everything works (motors, endstops, heated bed, etc), but the moment I turn on the extruder heater the ATX cuts out. I thought it might be my old ATX (350W), so I bought a new beefier one (500W) and the problem still happens. The ATX comes back after shutting off for a few minutes.

Has anyone had these kind of issues? Could my heater be shorting? Any suggestions on how to proceed would be greatly appreciated!

Here is a picture of my extruder assembly:


Thanks,
Rob

Nevermind! Found the problem - wiring mix-up in the extruder cable. Crossed wires led to a short before current even got to the extruder hot end. Swapped them and now the extruder heats up properly!