[mikedomi]

any video you connect to your laptop can cause a ground loop
put a 3 proung to two
adapter and lift the ground and if still there put it on the laptop too this will take cake of your problem
i am 99% sure of it and if it is still there
it my be comming from the tvs hooked up to the laptop

sorry but this is just the way it is
when they put the ac in the club were you are at some were along the way they crossed the wireing and that is the cause