[RojoRocket]

First thing I would do is flush all old brake fluid out with new, as it's possible you have a bit of water in the lines, freezing at night. Start by sucking all old fluid from the master cylinder (I use an old turkey baster) and refilling with fresh fluid, then bleed each corner until nice fresh fluid shows up in bleed hose. I'm sure others will chime in with their suggestions.
As far as the inside windows freezing, is it possible you have some water on the floor, under carpets, etc? Also check the spare tire well under the trunk floor for water. Lots of folks have had problems with leakage finding it's way in via tail light gaskets or missing/misrouted sunroof drains.

Glenn