I was having the same problem with the indicator for running programs not lighting up, plus command-Tab not switching between applications, plus the Expose function keys not reponding. Plus, logging out or shutting down was a nightmare (had to use the power switch on the computer to restart).
Using the Activity Monitor to quit the Dock process worked, but the dock did not automatically relaunch. Instead, the dock simply did not appear, Spaces was disabled, and restarting required using the power switch on the computer. Once I did restart *after* using Activity Monitor to quit the Dock process, however, everything is now working beautifully! (Before this fix, restarting the computer had had no effect.)
So, this is a wonderful fix! Just don't expect the Dock to automatically relaunch after you quit it.