[Zope] no accounts in root user folder?

Hello, I have a zope app in a folder and have an exUserFolder in there to authenticate the app's users. The app is working fine and i get authenticated by the exUserFolder and everything works. I tried to delete the single "admin" account (with Manager privileges) from the root standard user folder and the app breaks with: Unauthorized: You are not allowed to access 'call_backend' in this context where 'call_backend' is an External Method called by a Python Script. All objects in zope are owned by the "admin". Could this be causing the problem? Thnx for any help, Vangelis