Cmd+Tab not working

We're having this problem with a Mac Pro running OSX 10.8.4 and 6 monitors with dual graphic cards+Triplehead. The ⌘Tab window does not show and it doesn't switch applications.

I temporarily solved this using this guide by removing com.apple.finder.plist from Library/Preferences, but only for a minute before it reverted to not working again.

Any idea how to permanently solve this issue?

Solution 1:

The solution that worked for me was to open a Terminal window and type sudo killall Dock and hit the ⏎(=enter) key and then entering my password and then the ⏎ key again. It will take around 6 - 8 seconds for the Dock to 'die' and then be restarted. If your password is not working then you are not an 'Administrator' on the computer in which case you will need to obtain that password from the Administrator.