X11 cannot open display saga

[János]

Hi,

On my local OSX 10.4.9 machine  - 10.84.2.42 - ssh_config and  
sshd_config contain the X11Forwarding yes settings.

The remote machine - 10.48.106.84 -  sshd_config also contains  
X11Forwarding yes.

on my local machine I do:

bml0042:/Volumes/Home/janos janos$ xhost +10.48.106.84
10.48.106.84 being added to access control list

then I do:

bml0042:/Volumes/Home/janos janos$ ssh -X root at 10.48.106.84
root at 10.48.106.84's password:
************************************************************************ 
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*                                                                        
       *
*                                                                        
       *
*  Welcome to AIX Version  
5.3!                                                *
*                                                                        
       *
*                                                                        
       *
*  Please see the README file in /usr/lpp/bos for information  
pertinent to    *
*  this release of the AIX Operating  
System.                                  *
*                                                                        
       *
*                                                                        
       *
************************************************************************ 
*******
{[root]elm:/:852}#

According to the FAQ the -X or -Y should forward the DISPLAY over to  
the elm machine.  However when I try xclock:

{[root]elm:/:853}# xclock
Error: Can't open display:
{[root]elm:/:854}#

What else should be done ?

Here are the ssh related env variables from elm after the connection  
is established:

SSH_CONNECTION=10.84.2.42 49582 10.48.106.84 22
SSH_CLIENT=10.84.2.42 49582 22
TERM=xterm-color


on my own machine:
TERM=xterm-color
SHELL=/bin/bash
SHLVL=2
DISPLAY=:0.0


What else must be done for xclock to work from the remote elm machine ?

Thanks ahead,

János
P.S.  on my on local machine xclock works.