X-forwarding problem with Fedora 7

I am working on Fedora 7 and mostly use remote machines to submit my jobs and various pre and post-processing of CFD problems.

Last few days I faced a strange problem. While sshing the remote systems with X-forwarding(ssh -X user@host or ssh -Y user@host), it was successfully displaying the x-things on remote computer. While it was not able to do x-operation on IBM-AIX m/c. I did everything to make it including -

on server : xhost +
on client : export DISPLAY=server_host:0.0

but it was not able to display and while running any x-operation, it was returning this error-

xterm Xt error: Can't open display: localhost:0.0

I followed all advice on diftt forums including this great one ( http://www.oreillynet.com/linux/blog/2006/08/ ) which I thought should work but not [:-(].

Finally I found a solution which is as follows :

edit /etc/gdm/custom.conf on server
add 'DisallowTCP=False' just below '[security]'
restart the machine

Then do -

on server : xhost +
on client : export DISPLAY=server_host:0.0

and you're done.Run 'xclock' on client to check

You can do the same by running gdmsetup also I think(if you can't locate custom.conf)

Hope this will help