moisture in the car

I've got an 83 633 that is fairly mint, but there seems to be some sort of leak in the cabin. The windows are getting all fogged up and I am developing a serious mildew/mold prob. I know it's not rain getting in, so I'm thinking possible coolent leak. Is this common? Any ideas? Also if anyone has any info on real good bmw mechanics in the boston area, that wood be useful.

they most common interior coolant leak is from the hot water control valve right above the throttle pedal. remove the cover panel under the instr. cluster and have a look.....they're a little tough to replace yourself though due to the location of the retaining nuts on the water manifold it attaches to.