Silicone Spray - use, love it, keep it on hand. I sprayed this into the tracks on my passenger side window over a YEAR ago and I have not had any more problems with this window...

It is the easiest, and most time-effective solution around. You can go to the trouble of fiddling with the window innards, but you should only do this if the silicone spray doesn't work...

Brent
www.xanderstudios.com