Cannot wake Mountain Lion from safe sleep
I'm delighted to report that, after installing the OS X Mountain Lion v10.8.3 Update, this problem has gone away:


  About the update
  
  This update is recommended for all OS X Mountain Lion users and includes features and fixes that improve the stability, compatibility, and security of your Mac, including:
  
  [ deletia ]
  
  
  A fix for an issue that may cause the screen to display incorrectly after waking from sleep