You mean unhandled exceptions, don't you?
There probably was some global exception handler in asio or
boost.thread, which was removed later. I also rememeber such kind of
behavior change, though I don't remember what it was exactly :).

Actually I do handle all exceptions, but here it basically calls terminate immediately without giving me a chance to process it.

Strange thing that after erasing the library, pulling it again from our SVN then rebuilding the project seem to have solved this issue.