I had a really long post here - but my PC locked up, so I'll give the short version (which I'm sure you're grateful for):

Microwave oven seems to trip circuit breaker ONLY when nuking a potato. (And, no, I'm not leaving a fork in the potato or anything.) I remember doing an experiment in grade school with turning a potato into a battery, so I was just curious if there are some properties of potatoes that might cause this strange behavior from the microwave?

Any ideas?

It may be that the potato draws more power than other things you cooking. Is your oven one of the more complex ones where you tell it what you have put in it and it decides how long and how much power? If so, you might try a large pan of water and tell it is is a potato and see what happens. You might also try the water if it is a more simple one.

I hate that when I lose things like that. If I lose an answer, I never seem to be able to make myself write as nice of a one to replace it.