Apple's second firmware update for 27-in. iMacs seems to have fixed the flickering display problems, according to most users' reports on the company's support forum.
A minority, however, maintained that the update did not stop their screens from flickering.
Apple issued the second firmware fix in six weeks on Monday, saying it was meant to "address issues that may cause intermittent display flickering." In late December, Apple released a 27-in. iMac graphics firmware upgrade that was also pitched as a fix for flickering. Most users that reported the results of that update, however, said that it had not solved their problems.
This time around, the majority of users who posted their findings on the enormous support thread dedicated to iMac display problems said that Monday's firmware update had put an end to flickering.
"So after one night of having applied the latest firmware update, I have not seen any flickering," said a user identified as "jmczaja" on the thread. "Hopefully, the results will hold up."
"I have had the flickering problem from the start, and it was quite consistent in appearing every time the iMac had been turned on for about an hour," echoed Christian Hansen. "I could then cure it by letting the display sleep for a few seconds. After the update, which I did earlier today, I have not seen any flicker."
Some who crowed that the update had done the trick even called for the thread to be closed and the case considered solved, a move that raised hackles. "It is way too early to fully declare victory regarding the flickering issue, and this thread should remain open until such time when sufficient evidence has been presented, so that everyone is fully convinced," said Warren Beasley.
In fact, a small number of users -- fewer than half a dozen as of mid-day Wednesday -- claimed that the fix had done their iMacs no good. "Applied the new patch last night, and after a few hours, flickering started happening again," said Stephen Stark early today.
Whether coincidence or not, Apple this week reduced the delay between 27-in. iMac ordering and shipping from three to two weeks, and told the Wall Street Journal that it had never stopped production of its most expensive iMac, as a French blog asserted over the weekend.
Apple has been close-mouthed about the iMac problems -- not surprising, given the company's penchant for secrecy -- but it has commented publicly on two occasions, including yesterday's to the Wall Street Journal. Both times, Apple claimed that the delays in processing iMac orders were due to high demand, not because it had slowed or stopped the assembly lines so it could find the cause of the flickering problem.
Display issues have plagued Apple's 27-in. iMac desktop computers since the new machines debuted Oct. 20. Users have reported cracked screens, a yellow tint to the display, black banding and, of course, the irritating flickers.
Some owners of the less-expensive 21.5-in. iMacs have also complained of display problems, but the number of reports is much smaller than for the larger model.
Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer, send e-mail to firstname.lastname@example.org or subscribe to Gregg's RSS feed .