Turned out to be a silly problem in /etc/exports. If the server knows the requesting client by *name* - e.g. in /etc/hosts - then you have to include the *name* of the client in /etc/exports; the IP address doesn't work.

NFS versions? Dunno.
lockd? Yep.

Exports line: /home2/files 10.0.0.*(rw,root_squash,sync,anongid=401)
I duplicated the line and replaced the 10.0.0.* with the name of the client (and did exportfs -a) and it worked.

The mount command was: mount isengard:/home2/files ./files
which worked after I changed the exports list.

Thanks everyone, anyway.

Wade.

a) the fix makes sense (usually) b) the fix tends to stay fixed!

Wade.