This has happened to both doors on my 01. Basically, the locking mechanism inside the door gets stuck due to rust or grease/gunk buildup and won't unlock. The solution suggested here which I used successfully both times was to roll the window down and spray the inner door lock mechanism with wd-40, then rock the lock switch back and forth. Both times, within a minute or so, the lock popped free. I used the straw on the can of wd-40 and a flashlight to look down between the rubber window seal and to make sure I got the right parts. The long term solution was to take the door off (once unlocked), remove the inner panel and really clean and grease the mechanism to keep it from happening again. Honestly, since I did the simple fix (both doors over a year ago), I haven't had it happen again.
Jim