Another variation on basement wall painting

Hi all, I will be ripping my 60's era panelled, uninsulated, unheated basement out this spring. This is not the first basement I have done, but, I'm trying to avoid a problem I had experienced in the last basement refinish with moisture, and mildew. Basement is 3-4' below grade. The last basement I refurbished was also 3-4' below grade, with NO leaks, or water problems. to do the job right, I Thoro-sealed the entire basement....all walls, and floor. This Thoro-seal is supposed to seal the concrete. It is applied with a big paint brush, and dries like a cement. Well, I sealed the walls and floor, then used steel studs (2X4) for the walls, and installed 2" thick foil faced foam boards between the studs 16"OC, and put 1/2" green board up (Water resistant sheetrock). The walls were built out from the concrete foundation approximately 3-4". I also installed a new heating zone, then, installed 14' of High Output baseboard (hot water). The floor had moisture resistant padding with carpeting install over it. Then I put a drop ceiling in, good stuff, with foil backed 2X2 panels. I still had a dampness, and mildew problem down there. I then proceeded to rip out the new basement window (1 of the two NEW windows), and installed an air conditioner. It helped the moisture and dampness problem during the summer, but in the spring and fall, when your not running the heat or AC, the moisture problem came back. So, short of being relegated to running a de-humidifier (Which you probably guessed I am trying to avoid), what the heck can one do to insure this does not happen again? I went through considerable work and expense to insure the basement was well sealed and insulated, only to have it smell like damp, mildew. Yucch. The one difference between my old basement, and the one I will be doing now is, this house has Central air. The basement has a duct coming down to the basement, which supplies cool air, but it does NOT have another duct to the return air (Which I will do, cause it aint' working right if the air is not being exchanged). So, anybody out there see something I didnt do right to avoid this again? I'm certainly at a loss. Thanks!

How should I heat my basement after it is finished? Do most people just add a few additional vents to the existing HVAC system to "steal" heated air from the main part of the house? In my case I have two furnaces in the basement - one for the main floor, one for the upstairs. My thought was to add thermostatically-controlled vents into the basement from both systems so I can "steal" air from whichever one is running. Is this reasonable? Should I also be adding cold-air returns in the basement? Mike Wu