that stinks when that happens, does it only do it on the dirty channel? and what kinda pickups do you have(single coil,humbucker).if its doing it on the clean as well might be in your house wiring, or you may have a flouresent light or a computer monitor nearby.otherwise it may be like the other guy said and it seems it fixed his problem so that may be it either way i hope i helped and wish you luck in solving this because i know how annoying this can be.