I would guess BD may have overtightened the top bolt if you've never touched it; more likely than the small accident. That top cap pre-load bolt is meant to be tightened only enough to eliminate play in the headset/fork, it's defintely not meant to hold the stem in place, that's what the stem bolts are for. Riding for an extended period with top bolt too tight would cause pitting. Also fyi, top bolt should only be adjusted when the stem bolts are loose.

See
http://www.parktool.com/repair/readhowto.asp?id=65
and