The update, available on Apple's support site, addresses three times the glitches that version 10.6.1 covered.

Included in this update are fixes for a bug that unexpectedly logs out users, a problem that causes Mail to disable while setting up Exchange server and warn that an account has exceeded bandwidth limits, and a problem preventing authentication of an administrative user.

Other issues wiped away with the update is the distortion of web sites on Safari, the address book not responding during editing, a problem adding images to the address book, and not being able to open files downloaded from the Internet.

Hackintosh Users Beware

The Cupertino, Calif.-based company has a history of keeping tight control of its products, and this update is no different. Apple has displayed that control on several occasions, including when it twice stopped Palm from allowing Palm Pre users to sync with iTunes.

Apple has issued a warning about what the update will do to netbooks with Intel Atom processors that are running Snow Leopard. These are known in the Apple community as Hackintosh computers.

"You may experience unexpected results if you have third-party system software modifications installed, or if you've modified the operating system through other means," Apple warns on its support Web site.

Some users are opting for a less-expensive netbook in the economic downturn, but they want the power of Intel's Atom and the features of Snow Leopard. That has led to running Snow Leopard on Atom-based netbooks. Apple's update will wipe out the ability to create a Hackintosh -- at least for now. Observers think the removal of support for Intel's Atom is only temporary because the Hackintosh community will find another way to circumvent Apple's block.

Back Up First

Apple warns users to back up all files using Apple's Time Machine before installing the update. Time Machine lets users back up an entire system in Mac OS X version 10.5 or later. It copies everything on a Mac, including digital photos, music, TV shows, and documents.

The update with nearly 60 fixes and improvements can be run directly from Apple's web site. Users shouldn't interrupt the installation once the update has started, and Apple said the update size varies from computer to computer.

Because some updates are installed before others, Apple suggests users run Software Update more than once to be sure all updates have been made.