Updates issued by Apple last week did not fully solve lockup problems for some iMacs, and in some cases made the screen-freezing worse, Mac owners reported over the weekend.
Apple acknowledged it is again looking into the issue.
The two updates -- tagged as 1.2 for Tiger, 1.3 for those who have upgraded to Leopard -- are only vaguely described by Apple as "important issue fixes" that affect the 20-in. and 24-in. iMac models introduced three months ago. However, as users who pulled apart the updates suspected, they were designed to stop the lockups that have plagued iMac owners, said Lynn Fox, a company spokeswoman.
"Yes, they address the iMac screen freezing issue," Fox said. "We encourage all users to apply the fixes."
In early October, Apple acknowledged the lockups and said it was working on a software update that would be released "as soon as we can -- most likely later this month." Common characteristics of the freezing included inactive mouse and keyboard; continued background processing, such as music that keeps playing; and the need for a reboot even though the screen remains lighted.
Although some users posting to Apple's support discussions said the update had put a stop to the intermittent lockups, many saw no decrease in the frequency. "Freezing seems the same after installing the 1.3 update," said Paul Verhelst on this thread.
A few even claimed that the update had exacerbated the problem. "I updated and it actually got worse," said James Brancaccio on another thread dedicated to iMac lockups.
When asked if Apple is aware of the reports that the updates haven't stopped screen-freezing, Fox said: "We are looking into it."
Users experiencing lockups have never been able to agree o whether the problem is software- or hardware-related; the updates for Tiger and Leopard did not settle the issue, though some users actually felt vindicated when the patches didn't end the story. "This underlines my assumption of a hardware issue -- the iMac update 1.3 that I just installed doesn't help at all," said a user identified as tmo zoidberg. Fox declined to speculate about whether the freezes might be caused by something other than a software bug.
The lockup problem has been a hot topic on the company's support boards. One thread, for example, harks back to late August, includes more than 600 messages and has been viewed more than 33,000 times.
Last month, Apple tentatively fingered a mid-September iMac update, pegged as 1.1, for the problem. Previously, some users have said they were able to stop the lockups by rolling back Mac OS X 10.4, a.k.a Tiger, to their machine's original configuration.
The updates to Tiger and Leopard can be downloaded and installed using the Software Update mechanism built into Mac OS X.