Hi Danny,
It doesn't get much more tropical than Rio de Janeiro

, and I never had a problem with mildew on my cabinet.
Maybe your cabinet don't have enough non forced ventilation. It should have enough openings to keep it "airy" when the fans are not working.
Try cleaning the contacts with a rubber eraser. It sometimes helps with old memories.
Also, I heard it somewhere that you should not use memories with golden edges with mobos that have silver edges and vice versa. Supposedly the chemical reaction between the two different metals can cause problems.