Select All shortcut key Command+A no longer works This morning, I found out that the Command+A shortcut key for selecting all failed to work. I have gone into the keyboard shortcuts preference and did not find anything useful. Is there any suggestion on what to do to fix or at least troubleshoot my problem? Any help is appreciated. Thank you.
Reboot in Safe Mode and see if it works.

Here and here are some Apple support documents on Safe Boot Mode.