nfs mount problems

Hi,

I'm having a mounting problem with nfs, has anyone seen this situation
before:

- kernel: 2.6.18-53.1.4 - 64bit
- nfs version - nfs-utils-1.0.9-24
- clients mount ok with this in the fstab:

server:/export/share /nfs/share nfs
w,bg,nfsvers=3,tcp,timeo=4,rsize=32768,wsize=32768,hard,intr

some 32 bit 2.4 kernel client machines are getting an "input/ouput
error" when an ls -l is performed on the directory.

on the nfs server which is running v3 in /var/log/messages it's
showing "unknown version (3)" during mounts for all servers but it
does seem to be working ok.

has anyone run across this or seen anything of this nature?
.

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