One of our users, running a Mac with 10.6.6 and iCal (her account is set up within iCal as CalDAV), sent me a screenshot that when trying to accept a meeting invitation, she got a server error HTTP/1.1 409. Now I realize this is some kind of conflict message - is it possible that someone else is trying to add her to another event at the same time she's trying to accept this first one? How can we narrow this down?