So I'm on my way back from the lake, turn off the exit and begin to
stop - I hear this bang/thump from the back of the and the truck just
kind of lurched forward. I pulled over, stopped and got out to look
around.

Nothing on the road so I didn't kill anything human or animal. Stern
of the boat looks fine - nobody behind me and nothing fell off. Looked
the boat over, no holes in the hull, tire are fine, looked under the
truck, nothing there either.

Hmmm - oh well. Got back into the truck and started to the end of the
ramp - bang/thump, truck lurches again. WTH?

Got out look everything over, nope nothing. Hmmm - look up at the
front of the trailer and notice something dripping from the trailer
tongue - brake fluid. Oh oh.

Got back into the truck, pulled forward a little - bang/thump. Pulled
into the Wal Mart parking lot (more bang/thump), got out and
disconnected the trailer - I can move the actuator by hand. Open the
fluid resorvoir - not a drop - it's all dripping out the bottom. Ok -
got a problem. Locked out the actuator mechanically and got the
trailer hooked up and back home - no bang/thump but the damn trailer
and boat is heavy - 5,000 lbs and the truck takes time to slow the
load down.

Anyway, did the family thing, then took the tongue off the trailer and
much to my surprize..sure enough - theres my sign.

http://www.swsports.org/images/Solenoid.JPG

So I took the thing off the mount, but when I tried to take the brake
line off, the whole connector disintegrated into little flakes and I
was left with this.

http://www.swsports.org/images/Solenoid+line.JPG

Here's where it mounts.

http://www.swsports.org/images/Tongue%20mount.JPG

It looks like the actuator is ok, no rust or anything.

I guess I should have looked this over every year or so, but with just
under 14K miles on the trailer and it being ten years old with no
major issues other than disc and pad replacements (and one bad
caliper), it never occured to me to check the compnents inside the
tongue.

Lesson learned.

Now I gotta fund a brake release solenoid. And revamp the entire
system inside the trailer tongue system with rubber instead of steel.

Oy...