Looked again while reading this afternoon, and by pure geometry the only thing it could be is the collar. It's a big collar (oversized alluminum tubing thing), and a long ways down there so it doesn't seem so unreasonable. I'll try to chuck the bike up on a friends trainer for pictures, I just couldn't take any safely on the road that made any sense. In the meantime, I have half a bandana tied arround the collar.
Paul