firstly hire a proper electrician. He will have a thing called an Insulation tester and he will check every component on the machine separately for an earth fault.
However, I have come across this fault before and it has been the programme module that has been at fault.
DO NOT PUT THE MACHINE ON A SEPARATE POWER SUPPLY BECAUSE IF THE MACHINE DEVELOPS AN EARTH LEAK AND YOU ARE TOUCHING IT YOU WILL BE ELECTROCUTED!
FANTAZUM, October 2005