After you have installed and updated AirPort Utility, the application "AirPort Admin Utility" is renamed to "AirPort Admin Utility for Graphite and Snow".
AirPort Admin Utility for Graphic and Snow can be used to configure earlier AirPort base stations, but not to configure an AirPort Extreme (802.11n) base station. If you have one of these older base stations, you can still configure it using the AirPort Admin Utility for Graphite and Snow.