biff and comsat don't work

[Max <davros@cyclone.stanford.edu>]

I'm having a tough time getting biff to work properly.  I have the
following line in my /etc/services:

biff            512/udp         comsat

and the following section in my /etc/xinetd.conf:

service comsat
{
        socket_type     = dgram
        protocol        = udp
        wait            = yes
        user            = root
        server          = /usr/sbin/in.comsat
}

But I still cannot get biff to work even with "biff y"!  I tried
playing around with the MAIL and mail variables, but that didn't help
either.  All I want biff to do is to display the first 3 or so lines
of a new message as soon as it arrives.  Is there something else I
need to do?  The only error in the logfile that I can find is:

Nov  2 12:35:43 chinook xinetd[27596]: bind failed (Address already in use). service = netbios-ns

But netbios-ns is on a different port than comsat, so I don't see how
this should make a difference.

Thanks for any help,
    Max