Warren,
I had the same problem last month. Try changing the cable between the guitar and the amp. When I changed the cable the problem went away. I think in my case the ground wire may be defective. It is a Planet Wave cable with a life time guarantee. It will be returned on my next visit to Jacksonville. I hope this solves your problem also.
Guitars:
Electric: Washburn HB-30, Squier Tele Custom Deluxe, Jay Turser Strat.
Acoustic: Seagull S6.
AMPs: VOX AD30VT, Peavey Envoy 110.
Modelers: V-AMP 2, Digitech RP-100A.
Pedals: Boss RC-2 Loop Station, Boss CE-5 Chorus Ensemble, Digitech Bad Monkey, Ibanez DE7 Delay/Echo, DOD VFX40B 7-Band Graphic EQ, Ibanez CS-5 Super Chorus.