[Zope] Zope is not a valid NT app

Hi I tried Zope for a while in NT 4 Workstation, it worked smoothly after initial install. I stopped and tried to restart the server from inside Zope, now there is no way to get the service back. Even uninstalling (the service still appears in NT's services list, but can't be started, there is only a message "not a valid Windows NT application") and reinstalling. Ideas? TIA Marco