Start without the X port forward via ssh and get it working locally first.
If the X server isn't responding properly, trying to route it via ssh isn't likely to help
As the user that is running the x-server, see what the output to the xdpyinfo command is. That will tell you if you have an issue with the x-server itself or an auth problem.
Edit: hang on, are you running this locally or trying to run it over the network? Where is the X-server (the display) running?