BeamSync setting has ruined OSX Lion
When I attempt to read that value, I get told it doesn't exist:


  $ defaults read /Library/Preferences/com.apple.windowserver Compositor -dict deferredUpdates
  2011-09-28 11:44:23.535 defaults[4532:707]
  The domain/default pair of (com.apple.windowserver, Compositor) does not exist


IMPORTANT IMPORTANT IMPORTANT IMPORTANT IMPORTANT

You are about to make a serious modification. You should have backed up the relevant plist file before making any changes. But now, you should absolutely do so just in case you make a change that causes serious system instability.

MAKE A BACKUP OF /Library/Preferences/com.apple.windowserver RIGHT THIS MOMENT!!!!!!

Please don't do this until you have taken necessary safe-guards and understand what my command is actually doing. I suspect you may be able to restore the default by issuing:

defaults delete /Library/Preferences/com.apple.windowserver Compositor

I suggest this because I notice that in that plist file (/Library/Preferences/com.apple.windowserver), I have no reference to 'Compositor' whatsoever.