Apple has released AirPort Base Station Firmware Update 7.6.4 (http://tinyurl.com/l4mrhwd). It’s available for all Apple 802.11n Wi-Fi base stations including AirPort Express, AirPort Extreme, and AirPort Time Capsule. It contains fixes that:
° 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.