An update issued by Apple yesterday appears to have solved most of the screen freezing problems iMac users have been reporting since August, according to messages posted on support forums.
Targeting the newest 20- and 24-in. iMacs that sport the brushed aluminum casing, the Graphics Firmware Update 1.0 "updates the graphics firmware on the ATI Radeon HD 2600 PRO card to address issues that may have caused the computer to freeze," Apple said in a note accompanying the fix.
Apple first officially acknowledged the screen-freeze issue a month ago, but users began reporting the problem within a few weeks of the new iMac line's debut in early August. The lockups had common characteristics -- including an inactive mouse and keyboard, and continued background processing -- and the only solution was to reboot. Some users said their iMacs were freezing up several times each day.
The topic has been one of the most active of all those on Apple's support forums, with numerous threads, including one that as of today had more than 460 messages that had been viewed more than 27,000 times. Two weeks ago, Apple offered updated graphics drivers that it said would eliminate the lockups, but the problems persisted.
Yesterday, most users posting to support forums gave the new firmware update a thumbs up. "So far, so good here. Keeping my fingers crossed," said someone identified as bazmatting on the Apple site.
"Praise the Jobs, it's finally so far freeze-free (knock on wood)," said kkat69 on a MacRumors thread dedicated to the update.
A few who have lived with lockups, however, said that the update did them no good.
"When switching screen savers on the Desktop & Screen Saver menu, mouse stopped responding, just like it used to happen before updating the firmware. Seems that this firmware is a placebo or at least did not solve all issues," reported Ricky Avila in a pair of messages on an Apple forum.
Not all iMac users will need to install the update, Apple cautioned. "If you are not automatically presented with this update, your computer does not need it," the company said.
The update can be downloaded manually from Apple's support site, or by using the Software Update feature built into Mac OS X.