According to Apple Insider, despite the earlier Apple announcement that it was shipping iMacs within less than a week from the order time, the shipments of the 27-inch iMacs are now being pushed to three weeks, apparently due to demand and screen yellowing issues.

Even though the delay in the 27-inch iMacs’ shipments would likely be a deterrent for the best-selling desktop, Apple has not given any official explanation for the unexpected holdup, which is probably the longest one thus far ever since the October 2009 launch of the new model.

The company’s online store, which till Wednesday showed a one-week delay for dual-core iMacs for most part of this month, Thursday showed a three-week period between the 27-inch iMac orders and their expected date of shipping. However, the model is currently in stock with the US resellers, including Amazon. com and ClubMac. com.

Within just a few months of its launch, the 27-inch iMac has already been marred with a number of complaints about cracked screens, and an array of graphics issues, like yellowish-tinted screen and irksome flickering display.

Despite the fact that Apple issued a firmware update for all 27-in. iMacs last month, largely to address “issues that may cause image corruption or the display to flicker,” the users’ comments on Apple’s support forum are an indication that the update has not solved the nagging problems.