Update: It appears that Apple has removed the firmware download from their support site. As pointed out by David in the comments below, this update was likely not intended for public release just yet, as it was posted to the discussion thread by a customer who is apparently working with AppleCare to resolve the issue on her display. Remember, official updates from Apple will appear in Software Update.
Buyers of the 24-inch Apple LED Cinema Display who connected the device to Thunderbolt-equipped Macs were dismayed to find that the screen exhibited a flickering problem. The issue first came to light in February after the first Thunderbolt Mac, the early 2011 MacBook Pro, was released. Now AppleInsider is reporting Apple has released a firmware update to resolve the flickering issue.
The update notes state that the fix will only install when the display is connected to a Mac with the Thunderbolt interconnect, and that the update may not resolve the flickering issue if a Mini DisplayPort extender cable is used. There's also a warning to users to disconnect non-essential USB and FireWire devices while installing the firmware update, and to use only an Apple keyboard and mouse during the installation. The update is 926 KB in size, and works with Mac OS X 10.6.8 and later.
The 24-inch LED Cinema Display has been discontinued and replaced with the 27-inch Thunderbolt Display. The new display includes a built-in FaceTime HD camera, high-quality audio speakers, and support for Gigabit Ethernet and FireWire 800; it can also be daisy-chained to another identical display and other Thunderbolt-equipped devices.