Hi I am one of the experts here on Just Answer.com
This error can be for a couple of reasons .
First make sure you do not have both Entourage 2004 and Entourage 2008
running at the same time as this can cause an issue
If thats not the case you will want to check your Startup Items in System Preferences for duplicate daemons. If you have more than one, delete all and let Entourage create a new one when launched. Then launch Entourage to see if its fixed
If that doesn't work try trashing the preference file in your User's Preference folder:
com.Microsoft.entourage.database_daemon.plis and then reopening it
If that still doesn't work then the next step is to try and rebuild your entourage database
How to rebuild database:
Your Identity is located in Your User's Document folder inside the Microsoft User Data folder. First please see how big this file is and make sure you have enough free space on your hard drive to be able to have another copy of it.
This link here will show you where pretty much all the information is located if you look at number 1 a little down the page its where you can find your database file
Now to rebuild your database close entourage if it isn't already then Hold down the Option key and re-launch the application. In a few seconds, you¹ll be greeted with the database utility. You can rebuild the Entourage database by using the Microsoft Database Utility.
Please go through this rebuild if none of the above mentioned steps work for you and let me know the results
And please feel free to post any questions or concerns and we can continue working on the question
Edited by Omer Mushahwar on 11/12/2010 at 2:04 PM EST