I have /usr/pkgsrc exported via NFS like this from /etc/exports:
/usr/pkgsrc    -maproot=root -network 10.0.0.0/24

The client (10.0.0.3) mounts it like this from /etc/fstab:
arthur:/usr/pkgsrc /usr/pkgsrc  nfs rw,noauto,nosuid,-i  0 0

/etc/rc.conf on both machines has mountd, nfs_server, nfs_client, lockd,
statd, and rpcbind set to YES.  The client is set to do builds in
/usr/tmp, so when a build is done, a symlink is added instead of a
directory.  Now, whenever a build decides it needs to download something
into /usr/pkgsrc/distfiles, the write hangs with a process-in-disk flag.
From this point on, any accesses to anything in /usr/pkgsrc from the
client will also hang with a process-in-disk flag.  Same goes for umount
attempts.  Interestingly, rpcinfo -p client when done from the client also
hangs.

-- 
David Griffith
dgriffi@cs.csubak.edu