Just recently updated an office to osx mavericks. One user since then has had an issue with Calendar. The delegates constantly refresh, and the list is different every time. If I try and select a delegate it will appear on the calendar for a few seconds then disappear. I tried with a different user on the same machine and it works fine. I have tried deleting the cache of the calendar and also deleting and recreating the account multiple times.

Any idea what is causing this issue?