Chris,
I used to have terrible fogging problems with my old film cameras, especially in the summer when diving in Lake superior. I would drop to the bottom on some deep wreck and start to take some shots when I realized that my camera was totally fogged. At the end of our bottom time, and the start of some lengthy deco, it would finally clear and all we could do was shoot pictures of each other decoing out- my buddy had the same problem.
In the end we started to hang our camera systems over the side of the boat, at about 20', while we geared up. By time we finally rolled in and started down the line they would be cleared up and we could start shooting.
In the end it seemed that the warm, and humid, surface temps matched with the frigid bottom temps, even in August, caused all the problems. You can try and load your camera in an air conditioned room or use a little desiccant packet with it. I doubt that it's the housing itself.
Good luck,
Jon
