Hi alan,
I'm at the end of my tether with the same problem. My door seal was done to and still happening. This week they found a kink on the bulkhead heater pipe. They told me it won't come back, guess what, this morning carpets damp again! It's had 2 water tests and it doesn't sem to happen so i think it's gotta be coming from inside. If i find the answer i'll post you.
foxy, March 2009