This is for Exchange Server Enterprise 2003. Can anyone help me understand how and why this happens?

Hi, Here are some good articles for you, Description of common scenarios in which calendar in formation may be removed from the calendar or may be inaccurate: http://support.microsoft.com/default.aspx?scid=kb;EN-US;899704 Recommendations for troubleshooting an Exchange Server computer with antivirus software installed: http://support.microsoft.com/default.aspx?scid=kb;EN-US;245822 If the articles above cannot help you, please describe your issue more detailed. And I am glad to have a further discussion with you. Best regards, Serena Please remember to click “Mark as Answer” on the post that helps you, and to click “Unmark as Answer” if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.