PB,
Did you ever get this problem sorted out?
I did! Today! It only took me two months to get around to it. A trip to the hospital followed by a vacation, followed by a string of birthdays, then spring break and finally I got around to it!
It was a bad switch in my Generator transfer switch. I removed that circuit and wired it back into the main panel and everything is good! Except I need to replace my transfer switch since it has a bad circuit and I don't have any faith in it anymore.
I had reset the breaker on that switch (it's separate from the switch) but hadn't actually tried the switch. The switch wouldn't budge. I looked inside the transfer switch box and there was no sign of rodent activity so I think it was just a bad switch.
I did take the long road to finding this but I did use my Lan Tracker to trace the wires which was useful in finding the box that the wire lead to and to trace where the wires all went. I also bought one of those non-contact testers which was pretty cool too.
It's good thing I don't do electrical work for my career 'cause I would sure be slow.