Stefan
We have the same problem as we do not/cannot put userid and password into the url response (the storage of this information by UIM does not meet our security requirements.
What is happening is that any page on ITSM is a protected route and so if on any page you do not present a valid auth token you are redirected to the login page and this then does a 401 responce to do kerberos/ntlm authentication (SSO) and if the client responds correctly then you are redirected to the requested page, in this case the default user landing page. Now url_responce does not respond to the 401 and so you are left with this apparent error.
Either you provide a userid/password responce as
@David Michel suggests or you move to net_response to check TCP connectivity.
Regards, Andrew