Apple has released a firmware update for the LED Cinema Display that addresses intermittent audio issues some people have been experiencing with the new monitors. This update should not be confused with the release of the LED Cinema Display Software 1.0 update, which was released several weeks ago to enable audio and brightness features for the new displays.
After the audio features were enabled, a number of people found that audio would either become very faint or be silenced altogether, requiring them to unplug the display and reconnect it for the audio to function again. If this has been happening to you, the firmware update will address the problem.
To update the firmware, ensure both the display and its USB connector are physically attached to your system, and then either download the updater from the LED Cinema Display Firmware Update 1.0 Web page or run Software Update on your system.
The firmware update utility will install to the /Applications/Utilities/ folder from where it will automatically run and provide you with onscreen instructions for updating the firmware. Be sure the display is plugged into a reliable power source so it remains on and connected to the system during the firmware update. An interruption during a firmware update can result in malfunctioning or broken hardware. One option to prevent power loss is to plug your system and display into a UPS battery backup before applying the update.