kerberos de-authentication help

[Rad]

While checking out the CUPS web interface I managed to (very foolishly) turn on kerberos authentication. I would like to get rid of kerberos authentication, but I have no idea how to do it. When I unclick kerberos authentication and click on "change settings" I get the following error message: "401 Unauthorized
Enter your username and password or the root username and password to access this page. If you are using Kerberos authentication, make sure you have a valid Kerberos ticket."

I don't get any pop up windows that I can enter username or password. I have no idea how to proceed from here. BTW I have a macbook pro running OSX 10.5.8. Please help me fix my foolishness.
Thanks!