I have a user running OS X 10.6.8 and Office 2011 for Mac Outlook v. 14.2.3 . Previously this user was on Entourage with Office 2008 for Mac. We are using an Exchange 2007 server. This user is on a MacPro.

The problem is the user is frequently getting messages that the Outlook database needs to be rebuilt.  When then problem started this happened once a month. This became once a week and now is several times a week, if not daily.

Sometimes it happens when they open Outlook, other times it happens after they have been using Outlook for several hours.

Does anyone know what is causing this? What can be done to stop this from reoccurring?

Thanks in advance for any and all help.