There is a bug in Mountain Lion (10.8.2) where you go to click on a compressed file to unzip it and your system just hangs and wont unzip it, forcing you to force quit the unarchiver. Until they fix the bug, you can run this workflow to quickly kill the correct service. It will restart when you try to unarchive something again. Drop this into your ~/Library/Services folder and then you should see it in the Services Menu under every application drop down on the menu bar. If you don’t see the service appear, open Services Preferences and scroll down to make sure there is a check mark next to the same of this workflow.
Q: But wait, how do I unzip this if the reason I came here was to get my unarchiver working again?
A: You can either reboot or type the following into Terminal:
sudo killall -KILL appleeventsd
The actual workflow is an applescript that does the following:
do shell script "sudo killall -KILL appleeventsd" with administrator privileges
Here’s the source: