Further to the brackets on the door frame (there are two), there is a steel bracket glued to the bottom of the window that strikes the bracket on the door frame. This is near the front of the door.
With the window down, the bracket is directly behind the bass speaker in the door.
After nine years, the glue finally gave way and the bracket fell off and was found in the bottom of the door.
Symptom - door won't close because the window winds up too high and fouls the rubbers. The bracket on the far end of the door strikes the window lifting frame and luckily stopped the window coming out altogether.
Solution - take off the door panel (see
SLK Home Page under disassembly - not complete though as there are a few more cover plates to remove.
Remove the speaker. Retrieve the bracket from inside the door. Wind down the window (keep anatomy outside of the door frame or you will lose bits of you).
Reglue using contact adhesive - anything that binds glass to metal. I didn't bother removing the green glue as it seemed well bonded. For the Aussies, I used Tarzan's Grip glue in generous amounts. Time will tell if it holds.
Pictures below.