Sooooo glad I found this post! I just installed a new head unit and in doing so you have to remove half the dash. Anyways, today we rolled down the back window and left it down most of the day...this evening we decided to roll it up after locking the windows (because of an unruly child) and I couldn't figure out why the rear window would only roll up with the key in the rear lock.
Now I know.....window lock button = rear window too.
Thanks guys! You saved me some heartache of removing the dash only to not find the problem!