> error 55 is ENOBUFS.
> Maybe it's a problem with the ethernet driver, maybe it's just that you don't
> have enouth mbufs. Try to bump the kern.mbuf.nmbclusters sysctl.

Here is what I have:

kern.mbuf.nmbclusters = 8192

The ethernet device is:

de0 at pci0 dev 2 function 0
de0: interrupting at kn300 irq 40
de0: DEC DE500-BA 21143 [10-100Mb/s] pass 3.0
de0: address 00:00:f8:09:a8:0f
de0: enabling 10baseT port

What I've thought about doing is just using a cross over cable between
secondary ethernet interfaces and just allowing NFS traffic over that
network/interface.

Thank you for your response, I'd like a little more help if possible.

BTW, the secondary ethernet interface on that machine is a:

ex0 at pci0 dev 3 function 0: 3Com 3c905B-TX 10/100 Ethernet (rev. 0x30)
ex0: interrupting at kn300 irq 44
ex0: MAC address 00:50:da:22:98:b8
OUI 0x000000 model 0x0000 rev 0 at ex0 phy 24 not configured

The other machine (client) also has two 3c905B adapters.  If this is a
ethernet driver related problem (the previous bug report I posted about
suggested that as well) then I might just try using only the 3c905B's 
for NFS.