Why does spaces keep capturing keyboard input some times after switching spaces?
I find that killing the Dock only sometimes makes the problem go away. Usually keyboard input returns, but if I switch spaces using the keyboard shortcuts, the visualisation sticks around &amp; keyboard input is stolen again.

What I have found to work is putting the display to sleep. I've had the bottom right corner of the screen set to do that for ages, so it's quite convenient for me. I've never had this method fail; once the screen is awoken, the problem is gone &amp; doesn't return when I switch spaces again.

To me this suggests that the problem isn't actually in Dock, it's in the system's EventTap subsystem, the bit that lets stuff like Spaces, Screen Sharing, LaunchBar, &amp; Spotlight take keystrokes before the focussed application gets them. I've actually experienced a similar problem with Screen Sharing, where the system whose screen is being shared gets its keyboard input mangled if a modifier key is pressed on the viewing computer &amp; not released until Screen Sharing has lost focus. It's sort of the reverse problem, but it indicates that perhaps the Spaces problem is the EventTap framework getting stuck in a similar way, never sending the message that Control isn't being held down any more.