I moved to Australia from the US and took my Crate amp and Ibanez electric guitar with me. To deal with the 240 VAC, I needed a step-down transformer. So I have this setup: The ground connector of the socket on the 120 VAC side got weak and stopped making connection (Note 1). So the guitar floated. Problem is, I feel a mild shock when I'm touching a metal part of the guitar with my bare foot resting on the metal case of my PC (I live an exciting life). If I measure that voltage (Note 2), it's north of 100 VAC sometimes. Should an open ground cause this? What piece of equipment is at fault and how do I fix it? I'm unnerved that a simple open ground caused a voltage so high. The house's bond between neutral and ground is nearby and I'm sure it's good - I've just had it re-done and tested. Help much appreciated.