Apple offers Thunderbolt display flicker issue fix
Apple’s 24-inch LED Cinema Display has a flickering issue when used with Thunderbolt equipped Macs. Well, it does until you download and apply the Apple 24-Inch LED Cinema Display Firmware Update 1.0.
The 24-inch LED Cinema Display Firmware Update addresses an issue that may cause intermittent display flickering. This firmware will only install on the Apple 24-inch LED Cinema Display when it is connected to a Thunderbolt-enabled Mac.
That said, Apple’s warning that the update might not address the flicker issue when the 24-inch LED Cinema Display is connected to a DisplayPort Mac.
You can download the Apple 24-Inch LED Cinema Display Firmware Update 1.0 here.