Not familiar w/ the vapor barriers, but the sunroof drainage tubes getting plugged is a common problem.

http://www.xoutpost.com/bmw-sav-foru...-problems.html

http://www.xoutpost.com/bmw-sav-foru...y-x5-help.html

http://www.xoutpost.com/bmw-sav-foru...eavy-rain.html

http://www.xoutpost.com/bmw-sav-foru...d-console.html

Good luck.