Outlook Calander Acting Up

I have a user that can’t add/edit for that matter do anything to her calander. Everything else seems to be fine. She can send/recieve emails just fine and it just happened today. It looks like just her calander was effected. There isn’t any error messages, just nothing happens. She is setup on XP SP2 and we have W2K3 SBS running exchange. Any ideas? If you need any more info let me know I like to get answer sooner than later.
Thanks
J Barrett