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The software update is now available in the Mac App Store. People familiar with the latest build said it is identified as "12A206J."
Apple has reportedly informed developers that MacBook Pro model released in mid-2007 are not compatible with the new build. The issue is expected to be resolved with a future update.
People familiar with the build also said that an error occurs when using Fast User Switching, in which the desktop may appear white for several seconds. Problems are also said to remain with the share menu related to Mail and Twitter in the pre-release build.
Issues are also said to remain from the previous build, including the fact that Notes no longer sync with iTunes, and Java applets may not work in Safari. Apple also reportedly informed developers that QuickTime screen recordings can be corrupted when using machines with Nvidia graphics processing
Wednesday's update is the second issued for the third developer preview of Mountain Lion; the last update was supplied to developers on May 1.
Mountain Lion is scheduled to go on sale on the Mac App Store this summer. More on the next version of the Mac OS X operating system will be shown off at Apple's annual Worldwide Developers Conference, which will kick off on June 11 in San Francisco, Calif.