Apple is delaying shipping new 27-inch iMacs until it can figure out the cause of flickering screens and other display problems, according to reports from authorized resellers. About 10% of those who wrote to me have experienced difficulties.

Daniel Smith from the Land Down Under was one who did experience problems. Here's what he told me:

"I purchased an iMac in in Melbourne Australia and have since received a refund. The computer suffered, light bleeding around the screen, unusual humming noise but most notably the lower third of the screen was very yellow in colour. Three staff members at the Apple store denied ever hearing of the problem, but simply offered a replacement unit or a refund, which was great.

"I am, however, stuck processing 21MP files on a 20-inch G5 with iSight. As a side point, after spending hours doing a Time Machine reinstallation on the new iMac, I tested the two computers (G5 vs i5) in a direct side by side comparison. I set the 2 up exactly the same and opened the same RAW camera file on both, with the appropriate applications already open on both. The result was; G5 22 seconds to open one file in Photoshop CS4 and i5 a mere three seconds! And to think I paid $3000 AUD for my G5 some 5 years ago and only $2500 for the i5."

Rex Boyce's experience seems to be more typical for Macsimum readers. He says he received his iMac quad-core i7 a few weeks ago. It arrived in perfect condition, and has worked well since. Ditto the experiences of Gene Steinberg, the Tech Night Owl himself.

"I ordered mine with the Core i7 processor and 8GB of RAM on Nov. 24 from MacMall," he told me. "It arrived apparently undamaged on Dec. 2, the day after MacMall called me and told me to wait another week for it. The screen was not cracked. The image does not flicker. There is no yellow cast.

"It may well be there are some units that shipped with such problems, which may be typical of early production of any model that has a fair amount of new components. As to blaming the ATI graphics card for the stuff that doesn't involve broken screens, aren't we forgetting that there's a 21.5 inch version with the same ATI card (4670) as the cheapest 27 inch version? Or am I just lucky?"

We also have a 27-inch, i7 eval iMac here at the Macsimum offices. So far it's worked beautifully.

By the way, Gene and his family are facing some serious medical/fiscal issues. If you can help 'em out, it would be much appreciated. You can read more here.