there is an old thread from 2007, Bigkriss had the same problem. The seat belt latch plastic piece was broken and a plastic piece was inside
http://www.bimmernut.com/forum/5-ser...tner-clip.html
The missing pic of the clip in the old post I luckily saved on my PC, here it is
Imageshack - seabeltclip.jpg
How to access, see RealOEM.com Online BMW Parts Catalog
The backseats come out in 4 minutes, its super easy for you to reach the seal belt mounts
If I recall correctly you just need a 17mm socket.
Lift out the rear seat cushion, and the seat belt recepticles are right there.
In case the Driver's and Passenger's FRONT Seat Belts are slow to retract:
check where the belt enters the pillar. Be sure that the beauty cover has not dropped slightly down and is not pinching the belt. I've had this problem after an interior swap and it can be hard to notice and very frustrating.
http://i28.photobucket.com/albums/c2...eatbelt001.jpg
http://i28.photobucket.com/albums/c2...eatbelt003.jpg