I used to use Leopard Server for my office. We all had accounts on there, and we used iCal and CalDav so we could all subscribe to a few common calendars. It never worked perfectly. But now we don’t use Leopard Server anymore. It just didn’t really help us out very much.
In my iCal I’d subscribed to a master calendar from the server. I’ve deleted that account hundreds of times, and every time I restart iCal, it show back up! And of course it complains that the connection can’t be found. No kidding the connection can’t be found; the server’s not there anymore!
The fix
You can remove the iCal managed preferences file. It’s in:
Just delete it and restart iCal. I had to restart iCal twice before I noticed the ghost calendar disappear. But this should take care of it.