You need to turn on the noreservport option on the nfsd of your 1.3
box.  The problem is that the 1.2.1 boxes are trying  to send nfs requests
using non-privileged orts as the source of their requests.  The 1.3 server
wants to hear only from nfs clients who talk through privileged ports.  The
option noted above, which may be spelled wrong so see nfsd(4) and exports(5)
for the correct name, put into the /etc/exports file will fix your problem.
-Brian

On Mar 3,  7:57am, Len Burns wrote:
} Subject: Compatibility Problems between 1-3 1nd 1.2.1 when using nfs
} I just upgraded our web server to 1.3 i386, and have a strange problem.
} When I try to mount a directory from the 1.3 machine using a 1.2.1
} machine as a client, It appears to mount.  But, it does not show up in
} df, and if I try to cd to the mount point, I get a messages saying
} permission denied.  I can mount directories from other 1.2.1 machines,
} and can mount the directory from the 1.3 server with a 1.3 client.
} Any ideas what is causig this?  About the only option I see at this
} point is to upgrade all out machines to 1.3.  Undoubtedly we will do
} this eventually, but I would prefer not at the moment.  TIA
} 
} -Len
} 
>-- End of excerpt from Len Burns