Paul Laurens: Uhm, do you have a tuner or satellite receiver - or something else that's connected to an outside antenna or something else that might have a different ground potential - in your system? Because this sounds to me like a grounding problem - maybe you could try a filter (these are called Mantelstromfilter over here, but I don't know the English equivalent), then.
I had a similar problem with my system years ago because the vcrs were connected to the tv-antenna on the roof, which had a different ground potential. It completely vanished, after I had bought and connected such a cheap (< 20 DM) Mantelstromfilter between the antenna jack and the antenna cable to my vcrs. Computers can also cause similar problems. In addition, I don't know whether the polarity of the power outlets in Canada can be switched by just rotating the plug (as we can over here). Then you could try that with all the connected components, too.
Greetings from Munich!
Manfred / lini