nfs share becoms read only on mount but is read/write on host

i have several nfs shares on one rhel 5.2 server which are mounted on another rhel 5.2 server.
this is done so that I can tar the contents of on server file to the tape drive on the other server.

on the host
the directories are owner nobody (rw); group nobody (rw); other (rw)
etc/exports file:
/backup        *(rw,insecure,insecure_locks,all_squash)

on the mount side
the directories are also owned by nobody
fstab:
192.168.2.1/backup   /tapebackup  nfs auto,rw,soft 0 0

I have 4 like this, the first three work fine the fourth turns the directory and all files on the mounted server to read only
I tar the files to a tape and then untar the files to another directory and run a difference on the two files
the files that are read/only do not tar to tape or at least they do not untar, can't tell since the only way I have to reading the tar is to untar it and the files are not in the directory

why given my setup why would the files when you view them on the mounted side show up as read/only

gair