Apple probes iMac lockups

Computerworld - Apple Inc. said today it is investigating lockup problems with the newest line of iMac desktop computers after customers flooded the company's support forums with complaints this week.

Introduced two months ago in a lineup refresh, iMacs with the aluminum casing have been freezing under a variety of conditions, but common characteristics include inactive mouse and keyboard; continued background processing, such as music that keeps playing; and the need for a reboot. The screen remains lighted, however.

"Whatever was going on at the time continues, so if you were listening to music it continues to play," reported a user tagged as tekn0ph1sh on a thread that boasted more than 240 messages. "The mouse pointer moves, but you cannot select anything. Tabbing through apps doesn't work. Volume keys and brightness are also unresponsive. The cap locks button turns on and off."

Although the volume of messages citing freezing iMacs swelled this week, tekn0ph1sh's thread dated back to late August, about three weeks after CEO Steve Jobs launched the new models during an event at Apple's headquarters.

Theories abounded as to the cause, but many users are convinced that it would be traced to the iMacs' ATI Technologies graphics cards and drivers. Apple shifted to ATI hardware for its iMacs, and dropped its former supplier, nVidia Corp., with the August models. "I don't know why for certain, but I suspect that there is some interaction between some games, the [ATI] graphics card and the drivers for the card," said Al Van Malsen on the same thread as tekn0ph1sh.

Advanced Micro Devices Inc., which owns ATI, did not respond to a request for comment.

In a statement sent to Computerworld's sister publication Macworld, an Apple spokesman acknowledged the problem, and said it may have been caused by a September software update. "A small number of iMac users have made us aware that a recent software update issued by Apple can sometimes cause their iMacs to freeze, requiring them to restart their iMac," the spokesman said. "We are tracking down the root cause of this bug, and will issue a software update which corrects it as soon as we can -- most likely later this month."

The update the spokesman referenced, dubbed 1.1 and released Sept. 13, came with only a terse explanation that it provided "important bug fixes." Numerous users contributing to the Apple support forums mentioned 1.1, and some even claimed that they had solved the problem by rolling back to the original configuration. Others, however, disputed those accounts.

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