I have added some entries in Vista calendar and it stopped working. I have tried few things like deleting entries, restarting computer, adding entries again but this doesnt help. To be more precise it helps in some intent. When I delete entries from calendar it works fine, but why would I need calendar that can not be used to store reminders. Do you have any information about this Vista calendar problem?
There is one quick fix for this problem. I think you have accidentally turned on User Account Control. When this option is turned on Vista calendar, for some unknown reason, starts to behave as you described. Turn off User Account Control and calendar will work fine. I hope I have helped you.