This is just from personal experence, im not too sure whats wrong. But when i was driving my moms mini-van and goin down some winndy roads after that her car would squel in the front right brake when ever u were to stop or not accelerate...But what i would guess is that it's the belt, check it for any rips or freghness.
Hope this helps

heh, nvm...i see now that u are an expert MB mechanic, so im sure u would have known about the belt