I have encountered the issue which I have faced almost 6-7 yrs back. We have to do the installation of 10g iAS on one of the production server and we are not able to run any X-windows like VNC etc on that box due to missing packages on that server. But we do not have time to look around for unix guys and get this fixed.
So what are the options available to finish this task. This is how you can proceed. Look at the box where VNC is running, run the following from this box to the one where vnc is not running:
ssh -X targethost -l username
it will prompt for password for that user and Vola you are in. You have to have ssh daemon running on target host otherwise it will not work. We completed are job and hope this helps others to do their job on time.
Happy Troubleshooting !!!