Apple has released AirPort Base Station and Time Capsule Firmware Update 7.6.4.
The update is available for all Apple 802.11n Wi-Fi base stations including AirPort Express, AirPort Extreme, and AirPort Time Capsule.
AirPort Base Station Firmware Update 7.6.4
– 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
Note: This firmware update is for all 802.11n AirPort base stations.Thanks Radioactive!