I have the same problem in mine but I haven't tried to fix it yet.There are problems with earlier years and power windiows that may be related. The problem is more significant for power windows because there is no user feedback of the resistance, the window motor just pushes and some people have had their glass explode. There are recalls against some power window Matrix and VIbes for this, but no recalls for manual window onesIn the power windows cars, there are a couple of bolts that loosen up. There are lots of threads about the problem, but I'd say look at
http://forums.genvibe.com/zerothread?id=24086 where JohnC posted a word doc about how to fix the power window problem. THe differences between our cars and JohnC's write up are that we don't have the power window control and wiriing to deal with, but we do have to pull the manual window crank, and for that see K-NINE's tip in
http://forums.genvibe.com/zerothread?id=36570If you do dig into it and find the cause, please post what you find and how you fixed it.