GFCI tripping when plugging in 17B

[nugget]

- 2004 17B, one of the pioneers, i think it might be #10.
New to me, we've now had 5 nights in it since purchased thru Reace/Tammy in fall 08.

Before recent trip, I plugged into house power non GFCI to get the fridge up to cold. No problem.
Once at campground, the big cord from the trailer would blow the GFCI immediately upon contact. Tried it at the power post at nextdoor site, same thing. Neighbor came over and lent me his adapter to see if mine was faulty, but that did not solve problem.
Gave up, and then just used a spare extension cord to plug in the fridge only to AC GFCI at campground, and used battery power for lights in trailer.

Once home, the plug fails as soon as it is plugged in to two different GFCIs. I've turned off all breakers inside trailer and it still trips GFCI right on contact.
--I've read that GFCI are super sensitive.
--Some people say dampness in a plug inside trailer can cause this. All of the four plugs seem okay.
--only thing out of ordinary is the negative power terminal is a bit corroded. I've taken the battery off as part of my effort to try everything.
--I don't recall this problem before. I'm pretty sure that last year I plugged into the same GFCI to pre cool the fridge.

Unless someone has a great idea for me, then I'll have to take it to an RV tech. Weird, especially since I have turned off all the breakers inside trailer, yet still trip GFCI at the house.
Thanks for weighing in with ideas if you can.

craig