Unzipping files recently stopped working on my MacBook Air running OSX Mountain Lion. I found the solution to my problem on StackExchange: execute the following command in a Terminal: sudo killall -KILL appleeventsd Other symptoms / problems solved by this command: Opening downloaded files from Chrome is not working "Show in Finder" is not working Alternatively, you can kill the appleeventsd process in Activity Monitor: Source: http://apple.stackexchange.com/questions/70160/can-i-fix-things-so-archive-utility-doesnt-hang-on-all-zip-files