Besonders der letzte Punkt ist nicht ganz unwichtig (und bei mir selbst schon aufgeschlagen)
Q: I’ve just upgraded to Lion, and my events don’t display in iCal, but if I go to the MobileMe website, they do. How do I get them to display in iCal?
A: This happened to me a couple of weeks after Lion was released. Apparently, Apple turned off MobileMe syncing for calendars at some point. You’ll notice that Calendars no longer displays in the Syncing section of the MobileMe preferences. To turn on calendar syncing, go to iCal’s preferences (iCal -> Preferences), click on Accounts, then click on your me.com or mac.com account, and, in the Account Information section, check Enable this account.