Leaking water

Whenever I go through a car wash or really heavy water hits my windshield, water comes trickling down on the upper left corner. I noticed that there are some rust where the windshield meets the roof. But also the rubber around the back of the back window is coming off. Could that be the problem? How could I get the rubber border back on? Its hard and stretchy but now that is cold it doesn't stretch that well.

I've had the same problem (except rust), you'll have to glue the black rubber border back in it's original place, try using black silicone to glue the rubber and seal the space where the rubber doesn't stretch.

The best stuff to use is, 3M Super Weatherstrip Adhesive Yellow, part # 08001 found at most auto parts stores.

http://store1.yimg.com/I/premiumautocare_1824_6055010