SUN-Ultrix NFS problems

[Alan Butcher]

SYSTEMS: VAXserver 3900 with ULTRIX-32 V3.0  hostname: a YPSLAVE to sun system
	 SUN 4/260 with SUNOS 4.0.3  hostname: h    YPMASTER

Both are NFS servers and clients, there are no known problem with the
mounts from the Ultrix machine to the SUN machine.

PROBLEM 1)

I am able to mount files systems on the Ultrix machine from the Sun
machine at boot time from the standard rc.local file with no error, but
any attempt to access the files systems results in the following error

NFS geattr failed for server a: RPC: Authentication error

PROBLEM 2)

If I attempt to mount the file system after boot is complete I get the
following error

mount a:/usr00 server not responding: RPC: Authentication error; why = Invalid client credential
mount: giving up on: 
    /mnt

QUESTIONS:
1) Anyone have a solution? (I HOPE FOR AN EASY FIX)
2) What are the causes of RPC authentication error
3) Any suggestions on an approach to the problem, I have tryed most everything.

Alan Butcher
ab at cerc.wvu.wvnet.edu