Hi Greg, now I found some time to retry: I opened "Configure Publishing and Subscriptions", added "Subscribe to web calendar", then entered the webcal:// link to my public calendar and set the "Schedule for:" to me. Now OP finds the calendar but gives me some cryptic error message similar to the one before:
But actually, this was not what I had in mind in the first place: I was looking for a possible solution to sync my private calendar on MobileMe with OP. Because if I change to public sharing, my wife cannot see it on her MM-Account from within a browser. MM does not sync subscribed calendars. If it does not work, I am fine with that. Il like OP 2 nevertheless.