How about a really simple fix? Have you ever tried spray silicone in the window tracks? Mine ('03) has had this issue off/on since I got it. So has many others. This will *USUALLY* fix this problem.

One word of advice though. Don't keep putting the window that's giving you problems up/down until you at least try this. Too much hard work on that regulator (that we already know could be better) will break it and you'll then be stuck with replacing that. Using spray silicone in the tracks from time to time will all but eliminate the need to replace the regulators. I've never had to...yet (knock on wood!).

-G