NFS export (problems mounting on OS400)

Hi.

I exported a directory on my Fedora Core 4 (SE Linux running in Warn mode,
no IPTables, predefined ports for various NFS services - see below).

I mounted successfuly the export on IBM AS400 - OS400. The problem is that
I can only write in the mount point. When I do a 'ls', it outputs nothing.
However I can chdir in an existing directory (which I can't see on OS400).
When making a listing there, I'm getting an error.
I can 'mkdir'.

Any idea?

Additional info:
----
$ cat /etc/sysconfig/network
NETWORKING=yes
HOSTNAME=test.test.si
RQUOTAD=no
STATD_PORT=32765
STATD_OUTGOING_PORT=32766
MOUNTD_PORT=32767
LOCKD_TCPPORT=32768
LOCKD_UDPPORT=32768
RQUOTAD_PORT=32769

$ /usr/sbin/rpcinfo -p
   program vers proto   port
    100000    2   tcp    111  portmapper
    100000    2   udp    111  portmapper
    100024    1   udp  32765  status
    100024    1   tcp  32765  status
    100003    2   udp   2049  nfs
    100003    3   udp   2049  nfs
    100003    4   udp   2049  nfs
    100003    2   tcp   2049  nfs
    100003    3   tcp   2049  nfs
    100003    4   tcp   2049  nfs
    100005    1   udp  32767  mountd
    100005    1   tcp  32767  mountd
    100005    2   udp  32767  mountd
    100005    2   tcp  32767  mountd
    100005    3   udp  32767  mountd
    100005    3   tcp  32767  mountd
    100021    1   udp  32768  nlockmgr
    100021    3   udp  32768  nlockmgr
    100021    4   udp  32768  nlockmgr
    100021    1   tcp  32768  nlockmgr
    100021    3   tcp  32768  nlockmgr
    100021    4   tcp  32768  nlockmgr

/expdir
  WORLD(rw,async,wdelay,root_squash,insecure_locks)
----


On OS400:
----
> cd /mntpnt
  $
> ls
  $
> mkdir test01
  $
> cd test01
  $
> ls
  qsh: 001-0011 Error found getting current working directory.
  Input/output error.
  $
> cd ..
  $
> pwd
  /mntpnt
  $
----


Thanks and best regards,
Dezo