You cannot create "active" Workstations while goto is not installed.
You cannot set a workstation to active when no goto-plugin installed.
You are faced with this: "Es fehlt eine gültige LDAP-Server-Zusweisung!"
But you cannot set any LDAP-Servers until you've installed goto.
And there is a typo in the translated message.
(from redmine: issue id 285, created on 2011-06-17, closed on 2011-08-15)