We have received numerous tips regarding issues with OS X Lion resulting in Macs freezing after waking up from sleep. A thread on Apple’s Discussion forum about this problem already has over 12,000 views and more than 300 replies. The issue appears to predominantly affect 2011 iMacs, although some of the posters have reported freezes after waking up their MacBook Pros from sleep. The only solution is to hard-reset the machine by holding down the power button.

Another thread is filling up with complaints about Lion freezing at the login screen (disabling the switching graphics feature in energy presets doesn’t help). Regarding the first issue, user rubenlx described problems with his brand new 27-inch iMac running Lion:

The machine freezes randomly when starting to play videos, either on Youtube, Quicktime, iTunes. When it freezes, the mouse still works, but the machine doesn’t respond to any command, requiring me to hit the power button and restart the computer.

Another poster, likely a newbie to the world of Apple, complains:

This is ridiculous… Not a good start to a new OS system. Does this stuff happen at every update? I can’t even click on the Apple menu to force quit.

Other people report freezes when playing back video clips in iMovie, iPhoto, GarageBand and other apps. Moreover, the problem is persistent regardless of whether users have the latest version of Flash Player installed, or any version of it for that matter. This suggests a likely problem with the QuickTime subsystem which mostly handles video encoding and decoding in third-party applications, in which case either the 10.7.1 update or a graphics firmware update could fix this problem. Here’s a little trick to help alleviate the freeze after playback issue…

OS X Lion includes two new features that let you continue right where you left off in case of an intentional restart or a freeze. The first option available in System Preferences tells your Mac to restart automatically if your computer freezes and the other ensures the operating system reopens all your windows and applications when you log back in. And if you were using Lion-optimized software (such as Apple-included Lion programs and iLife apps) that take advantage of the new Auto Save, Versions and Resume capabilities, you won’t lose your work as apps will also reload up-to-date versions of your documents.

1. Enable automatic restart after a freeze

Open System Preferences from Dock and navigate to Energy Saver. Tick the “Restart automatically if the computer freezes” box.

2. Turn on Finder’s Resume feature

Choose Restart from the Apple menu and have the “Reopen windows when logging back in” box checked. Restart once to make sure Lion has sprung your open windows to life.

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