Apple has released an update for all 802.11n Airport Base Stations including the AirPort Express, AirPort Extreme, and AirPort Time Capsule. The AirPort Base Station Firmware Update 7.6.4 includes the following fixes:
Resolve an issue that may cause AirPort Time Capsule to report that the backup disk is in use
Resolve an issue that may cause an IPv6 Tunnel error
Resolve an issue that may intermittently cause a loss in Wi-Fi connectivity with iOS devices
The AirPort Base Station Firmware Update can be down
