When using the update agent I noticed it didn't select the package netscape-navigator, even though it is list under the Security advisories section on the website. It did download and install netscape-common and netscape- communicator.
The update agent is smart and only retrieves those packages you already have installed. If you have -common and -communicator installed, but not -navigator, then it won't upgrade that for you. If you DO want to be presented with ALL packages that are available, even ones you didn't previously have installed, please select the "Display all available packages" option.