While playing around with GeekTool 3.0, I managed to put in a bad shell command, that caused both GeekTool and System Preferences to become unresponsive.
Since I couldn’t launch the GeekTool preference pane without crashing System Preferences, there was no way for me to delete just the offending shell command. I didn’t want to trash GeekTool and reinstall, since I had eight other scripts (geeklets as they are called in 3.0) that I didn’t want to lose. I needed a way to just delete the one bad shell script.
A Google search turned up nothing, so I poked around the files on my hard drive — and I found the file that contains the GeekTool configuration: org.tynsoe.geeklet.shell.plist in “\\users\username\Library\Preferences”. I double clicked on the file and it opened with Property List Editor. I expanded the keys under the root, and found the key associated with the offending geeklet and deleted it.
I was then able to launch the GeekTool preference pane without a problem.