Strange threading issue with apache2 WITH_THREADS=1

I have been using www/apache2 with WITH_THREADS=1 for a long time on a
-current system. With a recent world upgrade, I start to get "Fatal
error Dead thread has assumed at line 158 in file
src/lib/libpthread/thread/thr_exit.c (errno = 0)" and httpd no longer
functions. Rebuilding kernel/world/libpthread does not seem to make
any difference, nor does rebuilding www/apache2 itself.

Any suggestions?

Jiawei Ye

-- 
"Without the userland, the kernel is useless."
               --inspired by The Tao of Programming