[Zope] Zope FTP through SSH1

Hi, I'm trying to tunnel FTP connections to a Zope server through SSH1 to ensure that passwords don't get sent in the clear. (I know the session will still be unencrypted; that's okay for now.) I've followed the instructions for doing so that are available at http://www.employees.org/~satch/ssh/faq/ssh-faq-5.html#ss5.6, and doing so I can successfully create an FTP session through an SSH tunnel. The problem is, once I've logged in, Zope won't let me do anything. It responds to every valid command with a single word: 'Unauthorized.' If I connect directly to the FTP server using the same login and password, all works well. Anyone here have any ideas why this might be? Thanks for your time and assistance, rob