I am getting only half voltage at a 120v electrical outlet. The outlet is on a GFI circuit, but the other outlets on that circuit are fine. I have tripped and reset the GFCI. It tripped and reset fine, but had no effect on the outlet in question. I have removed the receptacle and checked the voltage across the wires (black to white) and I only get half voltage there as well. The voltage from black to ground is 120V. Voltage from white to ground is 0. Does anyone have an idea what the problem might be?

Describe "half voltage", do you mean 60 volts?

Describe "half voltage", do you mean 60 volts?

Yes, it's about 60 volts. I'm using a Volt-Ohm meter that's not digital, so can't tell you exactly what it is.

The white neutral wire has a loose or corroded connection someplace in the circuit to cause this symptom.

You probably have an open neutral. Meaning it's being fed by some appliance or surge suppressor through the RFI filter. If you put a load (Light bulb) on that 60 V, it should drop to zero.