2000 Ford Mustang Air Conditioning lines iced up.

I've noticed a funny humming noise coming from underneath the hood of my Ford Mustang 4.6 liter convertible the last few days. Today I decided to open up the hood after driving home, and I saw that the entire air conditioning housing (looks like a 7" high X 4" dia. tube) as well as the lines going into it and coming out of it covered with at least a 1/4" of ice on them. When I turn the air on, it blows ICE ICE cold, and most times, it blows what looks like colorless, odorless fog. I'm really worried now, because since I've owned the car, knock on wood, I've had NO mechanical problems up until now? Please help, I'm hoping it's only a re-charge, or better yet, the cars belt, or water pump, I'm clueless, thanks for any assistance you can give me. Jeff