A few years ago I experienced problems with Mac Archiver under Mountain Lion and posted a fix related to permissions. Today Archiver again would not function and just hung when called. The following fixed the problem and is much faster. Start Activity Monitor from the Utilities folder in the Applications folder. Sort the list alphabetically by process by clicking on the process name column heading. Find the process “appleeventsd” and click the "force process to quit" button in the upper left of the Activity Monitor window. The process will return the next time you uncomress a file.