Apple has released AirPort Base Station and Time Capsule Firmware Update 7.5.2. You can obtain it via the Software Updates component of Mac OS X’s Systems Preferences app.
It requires Mac OS X 10.5.7 or later and includes the following fixes:
° General fixes to Wi-Fi base station stability;
° Fixes some issues with AirPlay streaming;
° General fixes with USB interoperability including connection to external storage devices;
° Fixes some issues with NAT port mapping settings;
° Disables TKIP security with 802.11n rates per the Wi-Fi Alliance specifications.