unkillable multithreaded stopped process

Hello,

We run a number of Asterisk soft switches under FreeBSD.  Lately, the
copy of Asterisk used for development has been ending up in a STOPped
state, unable to be killed or continued.  The problem is intermittent,
but always happens when Asterisk is asked to quit (via "stop" on the
CLI or SIGTERM).

  PID USER            F LOCK   WCHAN   TT  STAT      TIME COMMAND
 1497 _asterisk 10480181 -      -       ??  Ts     9:47.29 /usr/local/sbin/asterisk -U _asterisk

This only seems to happen under -CURRENT (amd64, dated Dec 28).  Machines
running RELENG_6 don't exhibit this behavior.  I haven't tested
RELENG_7.  Asterisk is installed from ports and run unprivileged.

The only similar problem I can find is an old PR:

http://www.freebsd.org/cgi/query-pr.cgi?pr=72979

Any ideas would be appreciated.

Thanks,
bw.