I have a little problem with the calendar: When I unblock a calendar for another user, he can enter new dates or delete older, but he can't change alreaddy existing dates. Could you tell me how to change that?

Unfortunately you can't enter dates by drag & drop. Is it possible to do that and will you do it? And why i can't add a file to a new event or task ? i can add only a link to a event or task.