X-Display back to Lucid won't open

[mpenda]

On Karmic, to allow an external machine to open an X-Window on a user's PC, one had to change /etc/gdm.conf and set DisallowTCP=false. That file is no longer there on Lucid. I tried making the change in /etc/gdm/gdm.schemas but that did not help.

Any ideas how to accomplish this now??
Thanks for the help.