I just had an issue with this last December, actually it was Christmas Eve and I went to leave my sister in laws house and did not realize that the drivers window was frozen shut. You can imagine what happens next a few curse words and some time in the freezing cold tearing apart the door to get the window back in the regulator and in the up position.
Anyways to get to the point, I also tried a few different things Epoxy, windshield adhesive and so on with varying results from a day to a week. Finally got tired of messing with it and had run out of ideas when someone suggested ULTRA BLACK RTV!
Let me tell you it WORKS!!!!! Be very generouse when "filling in the clips" (fill them full ) and let it tack up for about 5-10 min, put the window in the clips and roll up the window ( make sure it is all the way up ) Then UNPLUG the window motor and do not try to use it for at least 24hrs ( I made the mistake of not unplugging the motor and forgot about it what a PITA having to do it over ) It has now been holding great for 3 months and that window gets used alot because for one I am in the desert, and for two I am a smoker.
Hope that helps.