[boost] [thread][1.34] Assertion in tss_hooks.cpp

Does anyone have any idea why the following assertion: Assertion failed: attached_thread_count == 0, file ..\libs\thread\src\tss_hooks.cpp, line 157 should occur in one of the regex regression tests. It's unique to msvc-6, has only recently started occurring, and I can't reproduce it locally either, the regression log is here: http://tinyurl.com/yhgmam Many thanks, John.