Workspaces not switching automatically Despite the fact that I have told mission control under 10.8 to spaces when switching applications(to the key window), it does not appear to work.  In fact the only time spaces works is when I tell it to switch using keyboard shortcuts. This started happening only once I unchecked show dashboard as space.

The following symptoms also occur:
-Checking "show dashboard as space" does not re-enable dashboard
-Dragging windows to the side of the screen does not cause spaces to switch
-Keyboard shortcuts for mission control do not invoke mission control.

Mac OS 10.8
I've seen this intermittently for a few releases now. I fix it by restarting the "Dock" process (which handles Spaces/MissionControl) using this Terminal command:

killall Dock

I don't know how to do that via the regular GUI, sorry. And before you run that command, do killall -s Dock to see the processes which will get killed. If only the one "Dock" process is listed then you're good to go.  Hope this helps!