I replaced the threads->exit() with a return(0); and the crashes are still occurring the same way. From my understanding threads->exit() functioned the same as return(undef).
As far as the use of the cond_* functions, they are used internally in Thread::Queue, which was in use in the other thread you pointed towards.
I'm trying to work backwards from the apparent win32 VMem corruption resulting in the "free to wrong pool", to see what might have overrun some memory.
I'm usually a Unix programmer, so debugging under Windows is a bit out of my comfort zone.
Let me know if there are other things to try.