How can I unsubscribe from an event or edit an event that I am subscribed to in iCal?

I just added an event from the website last.fm and iCal went through this list of new tasks before it could be added, and now I am subscribed to this event. However, I wasn't looking to create a new "calendar," which is what seems to have happened, and I would like to edit the event to add it to an existing "calendar," but iCal says I cannot edit nor remove events that I am subscribe to. Does anyone know a trick or loophole to undo the subscription??