TODO: Create your own actions: http://docs.blacktree.com/quicksilver/creations/scripts
But that’s not to say there isn’t a way to do it from Quicksilver. You can find a script on the Quicksilver website at http://docs.blacktree.com/quicksilver/creations/applescript_create_event. Cut and paste it into a file and put that file in the directory ~/Library/Application Support/Quicksilver/Actions/.
Set the icon of the script and it appears in the QS pane.
have you got QS → Preferences → Advanced → “run commands in background” turned on? If you have turn it off and try again.
Action for large text Growl notifications: http://blacktree.cocoaforge.com/forums/viewtopic.php?t=4474