nfs error with openbsd 2.5

[Justin Grudzien <grudzien@atreides.alphachannel.com>]

Greetings,
	I am running openbsd 2.5 i386 on three identical pentium II 
systems. All three systems have 512 meg of ram and losts of disk space. I 
am running apache webservers on all three of them which use nfs mounted 
disks that are physically located on a sparc 20. Over the past two days I 
have had to reboot two of them several times because the netowrk on two 
of the machines becomes unreachable for a period of time. Most of the 
time the network fixes itself and no action needs to be taken but 
sometimes it does not. When looking at the console screen I am noticing 
the errors:

/bsd: nfs send error 55 error sending to atreides.alphachannel.com

atreides.alphachannel.com is the file server which is serving nfs to the 
three machines. To conclude with a description of the problem One machine 
is severly affected with it. As soon as that nfs disk is mounted I start 
getting errors. The second machine it happens once in a while. The third 
machine has no symptioms and has been running great since the day it was 
install. All three machines are identical in config and version of 
openbsd and they are using the same kernel build. I am hoping someone can 
help me decipher this error. Oh one more thing I forgot to mention. At no 
time EXCEPT when the network is down is nfs actually down.

Here is what I did...

I immediately looked at the server. I figured with an error like that it 
must be the server causing the nfs errors. However there are other 
machines besides these three that are mounting drives via nfs that are 
not having any problems. Also not all three machines are having the 
problem. One of them is fine and the other one I have not seen a 
reoccurance from when I rebooted. I then started looking at the clients. 
The worst machine did not get any better after a reboot so I talked to a 
few friends who suggested that it could be a resource problem. I 
increased maxusers and nmbclusters because I thought maybe I was running 
into a resource limitation. That affected nothing. I tried various kernel 
tweaks which also changed nothing so I decided to send this newsgroup an 
email. Any information you can give me to point me in the right direction 
is appreciated.
	Justin