ScOtty,
It would be about five years ago that I was working on two different jobs about the same time, and ran into a similar problem on each one. One job was a very simple set up, a CRT TV and a Digital STB, the other, a Projector, AV Receiver, Digital STB, etc. In both cases, when a light switch was turned off (various switches around the house, but always the same ones), the picture would freeze momentarily. In the second house, closing the fridge door would cause the picture to freeze!

I will add, both of the houses would have been at least 15 years old, after some discussions with an acquaintance I connected a capacitor rated at 275 volts, I can't remember how many micro farads, and it was obviously non polarising (someone will know the right term), and connected it across the offending light switch, no more problems. It allows the voltage to bleed off without causing a glitch. Never got around to doing the switch for the fridge light, I think the client used it as a excuse to buy a new fridge.

During a recent conversation, it was suggested that the offending light switches would more than likely have been in high usage areas and needed replacing. Doesn't explain why changing the Family room receiver stopped the problem though!