OP
trev
They often are, try unplugging it and retesting. If it clears then there's your problem, hopefully you won't have fried it. This is an example of why it's wise to do a test on 250v before the proper one at 500, they don't like it up emThere are no neons on the switches.
There is a tv amp in the attic, would that be spurred from lighting by any chance?