error/auth/auth ldap noconnect all
The error may be caused by a misconfiguration of the server name or bind dn.
This error can be a tricky one; if you use LDAP for all your authentication, once this error arises you may not be able to log into Moodle to fix it. The entries that need to be checked/changed in the case of this error can be found in the database table mdl_config_plugins for the plugin auth/ldap (for MSSQL2005).
The host_url value in particular should be checked to ensure the domain controllers LDAP are using are correctly set.