Apple's 27-inch iMacs have been quite popular, but have also had a fair amount of problems with the LCD monitors and video output, including displays flickering, discoloration, cracked screens, and issues with massive CPU usage when running some multimedia programs. Not all systems have been been affected by these issues, but enough have for Apple to be aware of them and start issuing fixes.
Last December Apple released a firmware update for the Radeon HD 4670 and 4850 which was supposed to address some of these problems; however, a reports of screen flickers still persisted. These problems with the iMac have been rumored to be the reason for the recent delays in the shipment and availability of the systems though Apple claims demand for the systems is the cause. While the delays have been inconvenient for some buyers, if they are at least in part because of the display issues then at least Apple is addressing the problem.
Currently, AppleInsider is reporting there is word from Applecare technicians that Apple is planning yet another software or firmware update to further address this issue. This fix is rumored to be released in the next few weeks, though we will wait and see.
Keep your eyes peeled, and we will report on any updates from Apple when they are released.