Hi Jim,
Are you using Kerberos with SAML 2.0?
Directly there is no relation between SAML 2.0 authentication and Kerberos/SPNego, only if you are using both for single sign-on.
Make sure that the correct SAML 2.0 authentication context is configured. Are you performing a password based authentication with SAML 2.0 or single sign-on?
Cheers,
Filipe Santos