[Jeff n Susan]

It certainly sounds like a Monty problem. If I could make a good guess, I think it sounds like maybe a bare wire to ground somewhere,
You could try to flip ALL breakers off, then one at a time you could turn them on in the Monty. When you flip the one that is causing the problem,it would trip the house one, or kill the generator. That would be the circuit that is the possible problem and help you drill down to find the problem. Good Luck!