Following numerous other updates from Apple this week, the company has released a firmware update for AirPort Extreme Base Stations and Time Capsule devices. This update addresses wireless performance issues and problems with creating Guest networks when using the 5GHz band. In addition, Apple has released an update to the AirPort Utility for both Mac and Windows machines.
Apple highly recommends you install the AirPort Utility update before applying the firmware patch to the networking hardware. The utility can be found at the following locations:
AirPort Utility 5.5.1 for Mac (10.24MB)
AirPort Utility 5.5.1 for Windows (10.70MB)
The updates for the utility address problems with importing configuration settings for the Base Station, and problems with the utility not propagating MAC address control lists when using extended networks.
The firmware update will bring the firmware version to 7.5.1, and will be available for download and install through the AirPort Utility. This can be set to automatically check for updates, or you can choose "Check for Updates" in the "AirPort Utility" menu.
For more information on installing firmware updates for AirPort base stations through AirPort Utility, including reverting to previous firmware versions, see the following Apple knowledgebase document: http://support.apple.com/kb/HT1218