Apple released a Mac OS X Leopard upgrade that brings better stability and security to the operating system and improves compatibility with AirPort wireless networks and other Apple technology.

Mac OS X 10.5.8 was made available from Apple on Wednesday through the Mac Software Update tool, as well as downloadable from Apple's Web site. The upgrade includes Safari version 4.0.2, the latest release of Apple's Web browser, which improves accuracy of Safari history search.

The OS upgrade also resolves problems around the disappearance of display resolutions in System Preferences, and fixes a flaw that could prevent the importing of large photo and movie files from digital cameras.

Other improvements include enhanced Bluetooth wireless reliability with external devices, USB webcams and printers. The upgrade also improves iCal reliability with MobileMe Sync and CalDav, and corrects data reliability problems between iDisk and MobileMe.

The upgrade improves compatibility with AirPort wireless networks. In addition, the software improves Sync Service reliability and RAW image support for several third-party digital cameras.

Also enhanced in Mac OS X v10.5.8 is compatibility with some external USB hard drives. Security fixes include updated bzip2 to prevent an unexpected application termination when opening a maliciously crafted compressed file.

In other security fixes, the software extends the system's list of content types that will be flagged as potentially unsafe under certain conditions, such as when the files are downloaded from a Web page. The software also corrects a problem in which signing out of MobileMe did not remove all the user's credentials.

Apple released a total of 18 security fixes.

Apple released the Leopard update as the company prepares to launch a new version of the OS called Snow Leopard. Officially called Mac OS X version 10.6, Snow Leopard is scheduled for release in September. The OS will offer significant improvements, including a performance boost as a result of Apple moving the platform over to a 64-bit kernel, which offers support for a virtually unlimited amount of system memory. The software will be priced starting at $29 for a single-user license.

Snow Leopard is available for pre-order on Amazon.com, where it was the most popular software on sale as of two days ago.

In addition to the Leopard update on Wednesday, the company released a Mac OS X Server 10.5.8 update that improves on the reliability of Time Machine backups, propagates file system permissions, maintains history of users' previous passwords and spotlights indexing and memory consumption.

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