Milter-greylist

milter-greylist sometimes spawns hundreds of processes that don't
terminate, consuming all memory then crashing the server.  Usually
it has 5-10 processes.  Sunday processes proliferated, a few more
every 5 minutes (a crontab job captures a snapshot of 'top' every 5
minutes), until there were 264 greylist processes then the server
crashed.  mail traffic had not increased.  maillog and greylist.log
don't record anything unusual happening - nothing different than
the usual day that has no problems and no time when greylist
has more than 20 processes at any one time.

What would cause this?  Can I configure milter-greylist to use
only a maximum number of processes?  Would restarting
milter-greylist dump old processes?