This error is due to a corrupt Outlook profile.
I solved it by taking the user’s profile off of Cached Mode (they didn’t need that functionality)
Simply goto Tools–>Account Settings–>
Open up the account and uncheck Use Cached Exchange Mode. Save and close and reopen Outlook.
This is the quickest fix for your user. If you want instructions on deleting and recreating the Outlook profile you can google that 🙂