Apple released an AirPort Extreme Update, 2007-004, on Tuesday. The update is "recommended for all Intel-based MacBook, MacBook Pro, and Mac mini computers and improves the reliability of AirPort connections," according to Apple.
No other information was released by Apple about the updater. It is small, only 745 KB.
A standalone updater can be downloaded from Appleis support site. It also appears in the System Preferences/Software Update of the above cited Macs.