Apple has released AirPort Extreme Firmware Update 5.4 which features:
– Improved antenna output control.
– Enhanced logging from your base station which is compatible with syslog.
– Performance improvements for WPA security implementations.
This version of the AirPort software requires:
– Mac OS X v10.3 or later
– An AirPort Extreme-ready computer with an internal AirPort Extreme Card or
– An AirPort-ready computer with an internal AirPort Card
Note: WPA requires an AirPort Extreme base station and AirPort Extreme or AirPort clients running Mac OS X v10.3, or later. Use of Wi-Fi Protected Access (WPA) reduces the maximum number of network users. Computers with wireless cards that only support WEP cannot join an AirPort network that has WPA enabled.
More info and download (4 MB) link here.