Cannot delete Live shared calendar

Question

I've a Microsoft live account. I use the calendar.

Actually I've following situation:

There's a unknown calendar, that has a recurrent event in it. The problem is that I cannot remove the event and/or the calendar. I'd like to remove it but in the custom menu as you can see I can only change color and charm, there's no commands for removing it. Same thing if I click directly on the event.

How can I remove it?