Along with the Keynote update, today Apple posted an update for the Graphite and Snow AirPort Admin utility. You can read more information about this Admin Utility update on the Apple support website; in a nutshell, it adds Leopard compatibility -- a good thing.
If you want to download the update, you can either open Software Update (Apple menu > Software Update) or download the installer package from the Apple support downloads site.
Note that he newer AirPort Utility (v5.3.1 or later) should be used for Time Capsule, and for AirPort Extreme or AirPort Express Base Stations. The update here is for the older base stations' admin tool.
Thanks to everyone who sent this in!