Most DSMs have this problem. Here are the fixes, courtesy of Tom Stangl (the VFAQ man), from a post in the Digest of Sept 25, 1998:
"The fixes are, in increasing order of difficulty
1 - Clean and lube the rubber channels in the window frame everywhere you can get to them without tearing the door apart. Do this by getting any rubber/vinyl cleaner, putting it on a rag, and wiping the channels until the rag comes out clean. This may take a LOT of cleaning. Then lube with NuVinyl, anti-static ArmorAll, or even dielectric grease (YES, this grease works well and does not gum up if put on VERY lightly and then rubbed off).
2 - Open up the door, and clean/lube the bottom section of the rubber channels you couldn't get to in #1. This will take raising and lowering the window to get all the areas.
3 - Check the bolts that hold the window to the window guide bar to make sure they are not loose.
4 - Loosen the bolts that hold the guide bar to the door, and move it forward or back to get the window to go up perfectly straight (not a lot of adjustment here, but it doesn't take much).
5 - Loosen the window guides (the metal brackets covered in bristly material) a little so they don't push on the window so hard."
Michael Reisin reported good results with using silicone grease of the type normally used on stock plug boots. He recommends greasing the window glass run channels in the interior of the door very well with this grease for a semi-permanent fix to the sticky window problem.
For those who are truly sick of the problem and don't mind using a little judicious force to set things right, Jeff Earl's solution involves bending the window track (only a little, so chill out) and removing a fastener that appears to interfere with the window operation.
Tom Stangl has a FAQ for this particular problem up now. Also try using the FAQ Locator to find it, or other FAQs on this problem.