current freezing with sendmail-msp sumitting to ipv6 ::1.25

Hi,

yesterday I tried to make the system's sendmail-msp submit to ::1.25
instead of 127.0.0.1:25 on an up-to-date FreeBSD-current installation .  
When injecting a lot of messages via bsmtp (rsmtp command) the system
freezes solid after putting about 10 to 20 into the mail queue and doesn't
even get as far as delivering them into the user's mailbox.  There are no
messages on the console or in the log files, the console doesn't respond
any more and only way to revive the system is a hard reboot. Reverting to
the old setting makes everything work fine again. Am I just doing it the
wrong way round[tm] or is there some instability with IPv6 in
FreeBSD-current?
-- 
bye, Micha
I hate forms!