Stuck I understand. They replaced #5 and over-tightened it breaking it off at the base in the head (and not telling me about it)
http://kissaneasylum.typepad.com/motorcar/2007/04/ouch_that_hurts.html
Needless to say, it was a "interesting" one for my now retired mechanic to straighten out.
I yearn for the MB dealerships of old