Mission control keeps crashing

This is annoying. For a few months now, periodically, maybe every few days, I'm unable to use Magic Mouse gestures or keyboard commands to bring up Mission Control. The only solution I've found so far is to go to the terminal and kill the Dock, which automatically restarts and bingo, everything works again. I'm not a newb to Unix-like systems but I've browsed through some logs and can't find anything there.