Consider the following scenario:
You use Microsoft Outlook 2010 to log on to a Microsoft Exchange Server 2010 mailbox.
You use the Add to Favorites command to add a public folder to the Public Folder Favorites list.
You close Outlook 2010.
You use Outlook Web App (OWA) to log on to the mailbox.
You close OWA, and then you use Outlook 2010 to log on to the mailbox again.
In this scenario, the public folder disappears from the Public Folder Favorites list of the mailbox.
Note This issue does not occur if you use Microsoft Office Outlook 2007.
This issue occurs because of an error in OWA. When a public folder is added to the Favorites list in Outlook 2010, an entry for the public folder is stored in the Common Views utility folder of the mailbox. However, the entry is removed by OWA, because it cannot validate the entry.
To resolve this issue, install the following update rollup:
2529939 Description of Update Rollup 3 for Exchange Server 2010 Service Pack 1
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.