Apple has released for the AirPort Extreme Base Station and Time Capsule; the new version is 7.5.2 and works only with the 802.11n base station models released starting in 2007. The base station update improves AirPlay streaming, fixes USB issues for attaching external hard drives or flash drives, and solves some NAT problems.
The most significant change is the removal of the TKIP encryption key type associated with Wi-Fi Protected Access (WPA) from use with 802.11n networking. The certified version of 802.11n should work only with the more secure AES encryption key type.
The update is available after launching AirPort Utility; you may be prompted to install the firmware update, or you can choose AirPort Utility > Check for Updates. The firmware updates also resolve.
Apple also released. The latest version fixes a crash, addresses a display issue with DHCP settings, and solves a problem in which the keychain failed to store the network password when a 5 GHz network was named differently than the 2.4 GHz network.
The update finally brings a tiny change to slightly older 802.11n base stations: the capability to add multiple MobileMe accounts for remote access to attached drives and remote configuration via AirPort Utility using Back to My Mac (in AirPort Utility, select a base station, click Manual Setup, click the Advanced button, and then click MobileMe).
Until now, base stations from 2007 and 2008—those from before the dual-simultaneous band models were released in 2009—were limited to a previous firmware release that lacked this feature. Apple told me that they intended to add this feature to the 2007 and 2008 models, but they told me this in 2009. This change may be minor, but it’s great to have all the models running the same release, and getting the same fixes.