Rear Window Defogger problems of the 2007 Chevrolet Equinox

When weather turns colder than approximately 50 degrees, windows become foggy. Defroster set at highest fan setting will not clear fog from windows. Constant musty smell in vehicle, particularly when using air conditioning or defroster. Had taken vehicle to dealership to remedy approx 2 inches of standing water in spare tire wheel well and was told cause was a "pine needle stuck in the drainage hole of the rear taillight housing"???? I believe that there is a serious problem with water leakage in this vehicle. Have researched and found a TSB pertaining to diagnosing water leakage. Took vehicle to dealership to address issue of excessive fogging, and was told they could not duplicate the problem. I find this ridiculous, as I experience the issue daily when temperatures drop below 50 degrees. This is a safety issue, as I constantly have to roll down all four windows before making any turns or changing lanes. When temperatures dropped to the 20's, fogging turned to a thin layer of frost covering all windows. Fogging takes place on windshield, all four passenger windows, and sidelight windows. This is a serious safety hazard and needs to be addressed. Suspect issue with a seal or breach of frame, etc. Water has gotten into air conditioning/defrost system and is causing a mold problem. Please address. Multiple complaints similar in nature found on your website and also via internet search engines.