How do I run an X program that is sitting on an X86 system over SSH into XDarwin on a OSX machine? I tried logging in and typing galeon & but it came back with GTK warning cannot open display : HELP
You need to enable X forwarding (if you want the X traffic to go through the encrypted tunnel). The server you are connecting to must allow X Forwarding, check sshd_config for X11Forwarding yes.
If the server has it enabled, you can run "ssh -X user@remote-host" and X traffic should be forwarded automatically. The DISPLAY on the remote host will actually be set to localhost:10 (or 11, or 12, etc...) but it is tunnelled through ssh to the display on the local host.
If you do this more than occassionally, either modify the ssh_config file to enable X11Forwarding for all clients or create a personal ~/.ssh/config file.
The man pages for ssh, sshd, ssh_config, and sshd_config should have all the information you need.
The following page should be helpful - it has quite a few new possible issues that can arise with "ssh -X" (including those that Dennis mentioned), as well as diagnostic tests and solutions: