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Command-Tab not working linked to Screen Saver engine hang

Some users have noticed a problem with the screen saver causing a conflict that prevents the command-tab key sequence for switching applications from working.

CNET staff
2 min read

Some users have noticed a problem with the screen saver causing a conflict that prevents the command-tab key sequence for switching applications from working.

Apple Discussions poster plague88 writes:

"I've started having issues with command Tab switching between apps not functioning after a certain amount of time? I believe it could be the screen saver and the "sudo killall Dock" in terminal does not remedy this problem."

When this problem occurs, e command-tab does not work, but the computer is otherwise functional. Users have suspected faults with the Dock (having tried force-quitting it with terminal commands), but after checking the activity monitor application to track processes running during the problem, users found that the "ScreenSaverEngine" is locked up and displays a "not responding" status. The screen saver prevents application switching functions from occurring, and the process hanging is most likely keeping this function from being released.

There are a couple of approaches to fixing this problem.

Fixes:

Kill the screensaver process It may be that this problem is only a one-time problem or something that does not happen very often. As such, the easiest approach would be to kill the screensaver engine. This can be done in Activity Monitor by highlighting the "ScreenSaverEngine" process and clicking the "Quit Process" button. If standard "Quit" does not work, using the "Force Quit" option should work.

This can also be done by restarting the computer, so unless users are in the middle of work and need the command-Tab functionality back immediately, the problem should correct itself the next time the computer is booted.

Remove the screen saver preference file This problem may be caused by corruption in the screen saver preference file, in which case removal of the file will be needed. The file is called "com.apple.screensaver.NUMBER.plist" and is located in the /username/Library/Preferences/ folder (the "NUMBER" is a string of characters that is the computer's MAC address). Removing this file should be all that's required; however, users can also try removing the screensaver-related files that are within the "ByHost" folder that is in the same user preferences folder.

Change Screen Savers It seems this problem can be caused by some third-party screen savers, perhaps if they have not been updated to work with the latest version of OS X. It is recommended to either update the screen saver if an update is available, or switch to another screen saver. Users should have the most luck with the built-in screensavers.

Resources

  • plague88
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