I thought I'd cc the list since this is sort of a weird, fun bug. Sometimes, when collapsing a message into single part, the C-T is horked up.
It starts as: Content-Type: multipart/related; boundary=xyzzy; type=foo ...and ends as: Content-Type: text/plain; boundary=xyzzy; type=foo Erk! Boundary? Type? What? Demonstration attached. -- rjbs