[Exim] Delivery over NFS

Hi

I am having a problem with a user who's mail is delivered over NFS. I get
the following bounce error message

This message was created automatically by mail delivery software (Exim).

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

  save to /dev1-dept/kevin/Mail/spool/general
    generated by kev@???
    failed to lock mailbox /dev1-dept/kevin/Mail/spool/general (fcntl):

Checking the FAQ it said to make sure that lockd is running on the NFS
client.. Which it is, so
any other ideas would be great.

Thanks

Jamie