/usr/src/UPDATING says you need to run
    src/etc/rc.d/preseedrandom
as part of the upgrading process - but this file has now gone from
FreeBSD-CURRENT, a couple of weeks ago.
http://www.freebsd.org/cgi/cvsweb.cgi/src/etc/rc.d/Attic/preseedrandom
Regards,
Brian.