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Apple has posted a potential fix for those experience flickering Thunderbolt displays and the fix hasn’t been publicly announced but has been provided to users seeking help on the issue at Apple’s Discussion Forums. According to the company’s notes included with the update, the 24-inch LED Cinema Display Firmware Update will only install when connected to a Mac with the Thunderbolt interconnect and Apple also warns that using a Mini DisplayPort extender cable may not resolve the issue. Users are advised to disconnect non-essential USB and FireWire devices before applying the 926KB update and the firmware requires Mac OS X 10.6.8 or later……………

Apple quietly released a firmware fix for the issue, although the update has not been publicly announced and its existence appears to have only been revealed to a small number of customers who have escalated their issues through Apple’s support systems.  A link (.dmg download) to the firmware update was posted to Apple’s discussion forums earlier today and a number of users who have applied the update have reported at least initial success with addressing the flickering issues. Users report having to reboot their systems and power cycle their displays in order for the displays to function properly after applying the update. Full instructions for installing the firmware update are also included in the documentation and it is unclear why Apple has yet to publicly issue the firmware update for all 24-inch Apple Cinema Display users, and thus users should exercise caution in deciding whether to apply the update and prefer to check with Apple support regarding their specific issues. From the description included in the download file:

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.

IMPORTANT: 
This firmware update may not resolve the flickering issue if a Mini DisplayPort extender cable is used. 

NOTE: 
Some USB and FireWire devices may prevent firmware updates from installing correctly; disconnect non-essential devices and use only an Apple keyboard and mouse to apply the update.

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