By AppleInsider Staff

Published: 10:20 AM EST

Apple Inc. this week began testing Mac OS X 10.5.3 Update, a third maintenance and security update to its relatively new Leopard operating system that already bundles over 75 bug fixes and code corrections.

The Mac maker on Thursday informed its vast developer community of the availability of Mac OS X 10.5.3 Build 9D10, a pre-release copy of the software update featuring a focus list spanning some two dozen core components.

Among those components in need of evaluation, people familiar with the matter tell AppleInsider, are AddressBook, AppleScript, Audio, Back To My Mac, Dashboard, the Dock, DVD Player, Finder, Graphics, iCal, Mail, Portable Home Directories, Printing, Rosetta, Spaces, Spotlight, Time Machine, and VoiceOver.

In a set of developer notes reported to have accommodated the update, Apple is also said to have listed 75 code corrections that have already been baked into this first external build, including two aimed at critical memory leaks within CoreAnimation and iCal.

Other fixes target Dashboard, iCal alarms and syncing, Installer App, Spotlight indexing, PDFs within the Preview App, Mail alarms, Spaces, Stacks and the Dock.

Mac OS X 10.5.3 is presumed for a release sometime in April or May.