Developer website: Apple
Apple LED Cinema Display iSight Firmware Update... This firmware update corrects an issue with the built-in iSight camera on the LED Cinema Display where the camera may not be recognized by applications. To complete the firmware update process, please follow the instructions in the updater application (/Applications/Utilities/LED Cinema Display iSight Camera Firmware Update.app).
For more information about this update, please see here.
Mac OS X 10.5.8 or Mac OS X 10.6.2.