I had corrosion in my printed circuit board of my Subal ND2 housing when I was shooting a D2Xs, but it was my fault. A bit of salt water dropped on to the board when I opened the housing. Since then I always carry a spare circuit board, hot shoe connector, bulkhead and have been more careful to prevent water drops from entering the housing. Do you think some moisture is coming in contact with your board?
I live on the other side of the pond and I have had no big problems with getting parts or service in the States. I use Reef Photo and they have been excellent.