Quote Originally Posted by pdc124

Is this just because the thing is running from the CD/RAM and runs out of resources with trying to run vncviewer and the encryption for the tunnel ?
I doubt it. Check that the tunnel is working correctly and that the remote VNC server is there by typing "telnet localhost 5901" on the client side (after the ssh tunnel is logged in and set up). You should see some kind of low-level prompt from the remote end, e.g. I get "RFB 003.003". If you see this then the problem is the vncviewer side, if you don't see it then the problem is the ssh/vncserver side.

BTW, telnet is a good tool for debugging TCP/IP connection/application issues like this and many other similar problems.