I just upgraded to Lion from Snow Leopard in my iMac, but for some reason Command-Tab is not working.
I already restarted the computer and checked the option (it was already checked) System Preferences / Mission Control and tick "When switching to an application ...", but still not working.
What can I do ?
There is nothing to enable. The option you checked has nothing to do with the application switcher.
You could look through the keyboard shortcuts and see if anything has hijacked that shortcut.
Try starting up holding down the shift key. That will start up in safe mode and disable any third-party programs that might be affecting it. It also does a disk check, so it takes some time. See if it works in safe mode. If so, try restarting normally and see if it still works.
If it works in safe mode, then it is likely you have something that is interfering with it.
As another troubleshooting step is to log in as another user. If it works there, then you have something in your particular user setup that is causing the problem. If it doesn't work, then it is a system-wide problem.
You are right, loging in with another user "solves" the problem. Thing is: I did an upgraded, not a clean install, so all my third party programs are the same (and command-tab was working back then).
However, I found out that command-tab was assigned to spotlight. But I only solved the problem when I disabled it and restarted the computer. Now switching applications works. Time to enable Spotlight and assign a convenient shortcut.
Thanks for your help!
Open up the Console app (in Utilities folder).
Look through the All messages list and see if there is anything that gives a hint at a problem with the Dock or SystemUIServer. (sorry, I can't remember offhand which process owns the application switcher and don't have time right now to hunt it down).
Lion is different than Snow Leopard. Just because something worked there doesn't imply it will continue to work correctly under Lion.
How to enable Command-Tab to switch applications
