updated 08:20 pm EST, Wed February 29, 2012
Alters graphic cards' firmware
Apple has updated Software Update and its support website with a small update called iMac Graphic FW Update 3.0 which it says will fix "a graphics issue that will cause an iMac to hang under certain conditions" for Intel-based iMacs running OS X Lion. The bug apparently exists inside the firmware for the graphics card in recent iMacs, as the company issued a similar update last June.
Intel Macs capable of running Lion have been in production since mid-2007 and have during that time sported a number of different video cards, but most relying on ATI Radeon video cards (with the exception of most of 2009, when the company switched to using the Nvidia GeForce 9400M or the GeForce GT 120 with the GT 130 as an option). The file is just 481KB in size, but Apple has on previous occasions warned that users applying the patch should avoid any risk of a loss of power during the update, as an interruption could cause the iMac to fail to boot up normally.
The patch supports all languages but can only be applied if users are running OS X 10.7 or later. It is available via Software Update on affected machines or can be downloaded from Apple's support website.