Today I tried to press the Command-Tab shortcut for the Application Switcher but nothing happened. Another thing that wasn’t working was moving the mouse to the edge of the display to make the hidden Dock appear. The keyboard shortcut to display the Dock wasn’t working either. If this happens to you, the way to fix all of these problems is to restart the Dock. Open the Activity Monitor (it’s in the Utilities folder), select Dock in the list, and click the Quit Process button (or choose View > Quit Process). In the confirmation dialog box that appears, click Quit. The Dock is one of those processes that restarts itself if it’s quit, so that’s all you should have to do. The Dock and Application Switcher should both work now.
Not everyone is aware that the Dock hosts many processes in Mac OS X. For example, in addition to running the Application Switcher, the Dock also runs all of the Dashboard widgets. That’s why the way to make all Dashboard widgets quit is to quit the Dock. (When you simply exit Dashboard, its widgets don’t actually quit—they keep running invisibly in the background, taking up RAM and CPU power.) You can see how processes run within each other in Activity Monitor if you click the Show pop-up menu at the top of the window and choose All Processes, Hierarchically.
Now, of course, you can also fix this by logging out and back in, or you can restart the entire computer. But I often work with a lot of programs and documents open, and that’s why I look for ways to fix problems without having to close all my programs and windows and then set up the entire workspace again.
conrad chavez | blog 
Worked for me – Thanks!
Helpful, thanks.
Very helpful. Never would have come up with that. (Found you through Google.)
Thanks!
Ahh… relief! Just had this problem. Thanks for posting this very helpful tip.
How do you stop it breaking in the first place – having to restart Dock all the time is driving me nuts
Normally, the Dock and Application Switcher should just keep running, and I don’t know of anything that’s specifically known to break them. If they need to be restarted regularly, something unusual is going on that needs to be isolated through standard troubleshooting. There might be software installed that’s conflicting with the Dock. Make sure you’ve updated to the latest versions of any utilities that interact with the Dock or Application Switcher. Another idea is to reset the Dock preferences by deleting home/Library/Preferences/com.apple.dock.plist, but if you delete those preferences you’ll probably have to redo your Dock icon arrangement and settings.
so awesome…worked great!!!!!!!!! My day just got better.
If it keeps on freezing after killing and restarting, check Parallels – there is an issue with sharing Windows applications to the Dock that can make it go crazy. You should run Parallels and disable Windows Application sharing to the Dock for each virtual machine.
This might also be an issue for VMWare Fusion.
Awesome. Thanks!
Thanks!
My experience is that the Dock might be supposed to restart itself, but it often doesn’t. If you open System Preferences > Dock, sometimes that’ll do the restart.
Excellent tip! Thank you!!!
It worked. Thank you.
I could see my dock but was not able to open anything from it (clicking applications and nothing happened). This worked for me as well! The only problem I ran into is that I didn’t know where to find the utilities folder and I the only way I know how to get to my finder to search for it is my dock. But I found a way to get to it through my recent items in the menu bar.
Thanks!!
For future reference, an easy way to open the Utilities folder is to go to the Mac Finder and choose Go > Utilities. You can also use the Spotlight search feature to find Activity Monitor directly.
thank you so much! probably would have payed a good amount of money to the tech guy to help me out! great 👍