On Sun, 4 Sep 2005 13:02:12 -0400
Jan Schaumann <jschauma@netmeister.org> wrote:

> Well, the thing that really gets me is that this is a system that has
> been working fine for the longest time.  The filesystem hasn't changed.
> 
> I just can't make any sense of this.

Do you have all the required daemons running?

For NFS server you need to have the following in /etc/rc.conf

nfs_server=yes
mountd=yes
rpcbind=yes
lockd=yes
statd=yes

For NFS client you need

nfs_client=yes
rpcbind=yes
lockd=yes
statd=yes

Reboot the machine and the NFS should work...