ASMEURER I you have the Terminal open all the time like I do, it is much easier to just type killall Dock whenever the Dock, Spaces, the Program Switcher, Exposé, and/or Dashboard (yes, these things are ALL part of the Dock) go bad on you. The problem it that it is often impossible to do anything when some of these things freeze. What is really needed is a keyboard shortcut to restart the Dock that will work even if, for example, you are stuck changing Spaces or in Exposé and you can't do anything with any window.
(Version 1.0)