When logging in via Kerberos authentication, your tickets are not delegated (forwarded) to the new server. You'd have to obtain new tickets if you wanted to use them for authenticating with other services. It would be nice if we could offer the choice to delegate the Kerberos credentials to the ThinLinc server to avoid this extra step, and to offer a Kerberos-based SSO solution.
*** This bug has been marked as a duplicate of bug 4712 ***