Apple has delayed shipping new 27-inch iMacs until it can figure out the cause of flickering screens and other display problems, according to reports from authorised resellers.

The move came just days after a web designer created a site that tallied issues with the 27-inch iMacs , including screens broken in shipment, on-again-off-again flickering displays and screens that showed a jaundice yellow tint.

Two Apple resellers, independent dealers approved by Apple to sell Macs, contacted the Apple iMac (Fall 2009) Issues site to report that all shipments of iMacs had been pushed back at least two weeks as Apple replaces the machines' graphics cards.

Canadian web designer Scott Pronych built the tracking site after he received a 27-inch iMac with a shattered screen, saying he wanted to document the display problems. By digging through Apple's support forum and taking reports directly from others via a form on his site, Pronych has identified more than 600 users who have had issues with their new machines.

A thread on Apple's support forum dedicated to the flickering screen problem boasts nearly 1,200 separate messages and has a view count of over 173,000, making it easily the most read of those on the iMac forum.

The resellers who contacted Pronych are in Europe. "I think they are feeling a bit frustrated as a lot of customers are blaming them for slow delivery, and likely they see my website as proof that there are some real problems with the graphics system of the new iMacs," Pronych said.

Pronych reached out to the resellers, but both declined to comment on the record. "I don't want to hurt my ties with the Mac community," one of the resellers said in an email to Pronych that he forwarded. "As you may or may not know, Apple is strongarming resellers since opening their own Apple Stores," the reseller continued.

Earlier this week, Apple changed the shipping status on its online store for both 27-inch iMac models from "Ships: 5-7 days" or "Ships 7-10 days" to "Ships: 2 weeks." Although high volume sales could account for the change, Pronych said he had been told by some users that Apple had pushed back the projected ship dates for their already ordered iMacs.

Both the dual-core and quad-core iMacs are affected by the flickering screen issue, according to reports filed with Pronych's site. Those models use AMD's ATI Radeon HD 4670 and Radeon HD 4850 graphics cards, respectively.

The 27-in iMacs were introduced in late October, when Apple refreshed its desktop lines. According to Pronych's data, fewer than 10% of the total reports are from users of the less-expensive 21.-5-in. iMacs. The entry-level $1,199 machine uses the NVIDIA GeForce 9400M integrated graphics chipset rather than an ATI graphics card.

Apple has not responded to multiple emails asking for comment on the 27-inch iMac screen issues, including one requesting information about the two week shipping delay. Apple typically refuses to comment on hardware issues, preferring instead to quietly publish a support document to its site.