nfs server issues

I have googled and seen a great deal of talk about FreeBSD nfs client
issues, but haven't seen anything about server problems.  I've now tried
with a Solaris 2.7, HPUX 11.11, and 2 different Linux boxes and I get
the same thing happening...

If I mount an nfs partition on any of the above mentioned machines,
everything works fine until I try to copy a bunch of files over.  For
instance, if I mount it at /mnt and do

cd /localdisk; (cd /mnt; tar cf - .) | tar xvf -

It will lock up hard.  Linux is saying

nfs: task xxxx can't get a request slot

It is only the one mount point that is effected, though.  The same
machine is serving accounts from ldap and is providing /home.  All that
still works!

My (I think relevant) processes look like:
    0    46     0   0   8  0     0   12 -      SL    ??    0:00.00  (nfsiod 0)
    0    47     0   0   8  0     0   12 -      SL    ??    0:00.00  (nfsiod 1)
    0    48     0   0   8  0     0   12 -      SL    ??    0:00.00  (nfsiod 2)
    0    49     0   0   8  0     0   12 -      SL    ??    0:00.00  (nfsiod 3)
    0   480     1   0   4  0  1368  944 select Ss    ??    0:00.04 nfsd: master
    0   482   480   0   4  0  1252  764 -      S     ??    0:00.67 nfsd: server
    0   483   480   0   4  0  1252  764 -      S     ??    0:00.19 nfsd: server
    0   484   480   0   4  0  1252  764 -      S     ??    0:00.01 nfsd: server
    0   485   480   0   4  0  1252  764 -      S     ??    0:00.00 nfsd: server

    0  1018     1   0  76  0 263620 1044 select Ss    ??    0:00.08 /usr/sbin/rpc.statd
    0  1023     1   0  76  0  4356 3084 select Ss    ??    0:00.08 /usr/sbin/rpc.lockd
    1  1024  1023   0   4  0  4328 3060 select S     ??    0:00.02 /usr/sbin/rpc.lockd

I thought it was the lock daemon, but I disabled it and the problem
still occurs.

I just tried the following to see if I could get anything else of
interest:

1) On Linux box, I did an "ls -lR" on my /home/sean directory (many
files).
2) On FreeBSD box, watched CPU usage of nfs processes and noticed which
was serving the request.
3) Waited and output finally hung.
4) used gdb to break into the process:

	(gdb) bt
	#0  0x280c934f in nfssvc () from /lib/libc.so.5
	#1  0x0804aaa2 in close ()
	#2  0x08049549 in close ()
	#3  0x08048bb9 in close ()

5) Noticed Linux box spitted out (server is my FreeBSD'd name)

	nfs: server server is not responding

6) quit gdb and Linux box said

	nfs: server server OK

7) access still hung and the ls command cannot be stopped with ^C.

Please let me know what I can do to help track down this problem.

Cheers,
Sean