Can't turn on extruder heater (no replies)

I know this is a common problem, and there are plenty of resources already out there, but for the life of me, I can't figure out what's wrong. The extruder resistor is plugged into the right pins, I've checked for any breaks in the wire, or if the resistor has burnt out. That's all fine. The heat manager is enabled, and when I turn it on, Repetier is telling me it's being fed power, but when checked with a multimeter, there is of course no voltage. It gives me no errors when starting up or turning on the heater. I had the heater working earlier. I even tuned the PID manager, but after I calibrated the axes, it just didn't want to turn on. The thermistor also function correctly. My setup is as follows:

Mendel Prusa + printrboard
Repetier firmware + Repetier host
Windows 7