The updates, released Thursday, are recommended for 20-inch and 24-inch models with 2.0 GHz and 2.4 GHz Intel Core 2 Duo processors and with the 2.8 GHz Core 2 Extreme processor. The name of the updates, which are on Apple's Web site, are Software Update 1.3 for Leopard, the latest version of Mac OS X; and Software Update 1.2 for Leopard's predecessor Tiger.

Apple acknowledged in early October that it had received complaints about iMacs freezing up suddenly and becoming unusable. Users had to reset the machines to bring them back to life.

The iMacs affected by the problem were introduced in August, along with new versions of Apple's iLife and iWork software suites. The machines are encased in aluminum and glass for easier recycling.

Apple had said the flaw affected a small number if iMac users, but that didn't help those who found themselves having to restart frozen new computers. "I decided to switch to Mac after seeing the pretty new package and now have buyers' remorse," a customer wrote in August on Apple's online discussion forum.

Apple is advising customers to update their machines either through the company's automatic update mechanism or a download from the Web site.

Apple heavily markets its computers as simpler and more user friendly than computers running Microsoft Windows, but lately Apple has had to deal with its own problems. Last month, the company posted a fix on its Web site for a serious flaw that caused its Mac computers to seize up when users attempted to upgrade to Leopard, officially known as OS X 10.5. Leopard was released Oct. 26.