Ars Technica summarize a problem with an App Store server that generated faulty DRM code for several days, causing downloaded Mac and iOS apps to crash on launch and users to hit developers with angry 1-star reviews. Apple has fixed the problem, which affected at least 120 apps and tens of thousands of users who downloaded updates or new apps during the time the problem occurred. Apple also reset the version numbers of affected apps to conceal (but not remove) the angry 1-star reviews. If you downloaded any apps around 5 July 2012, it’s worth checking for updates again. follow link
Find Your Mac's Serial Number
Want to check your Mac's serial number quickly and easily? Select About This Mac from the Apple menu, and click on the text directly below "Mac OS X" that reads "Version 10.x.x." Click once and you'll get a build number which is more specific information about the software. Click twice, and you'll get your Mac's serial number.
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Apple Fixes Crash-Causing App Store DRM Error