I'd try reinstalling X, then getting the Netscape installer deb package (there used to be one, you have to grab netscape off a Netscape site then install the .deb).
You can reinstall packages by having the .deb file available (in the current working directory, or append the path to the file name) then using dpkg -i <deb file name>. My guess is you will need to reinstall xbase and your xserver. Pat
