When going to the page listed, Safari from 10.4.9 auto fills the username and password entries properly. The nightly build failed to do so.
This is a known incompatibility between development Webkit and Safari 2.0. See http://trac.webkit.org/projects/webkit/wiki/Known%20incompatibilities%20between%20open-source%20WebKit%20and%20Safari *** This bug has been marked as a duplicate of 6877 ***