Assume that you upgrade Microsoft Office Outlook 2007 to Microsoft Outlook 2010. When you start Outlook 2010 and try to connect to Public Folders, you receive the following error message:
The set of folders cannot be opened. The attempt to log on to Microsoft Exchange has failed.
To resolve this issue, apply the following update:
2584053 Description of the Outlook 2010 hotfix package (x86 Outlook-x-none.msp; x64 Outlook-x-none.msp): August 30, 2011
Note You must start Outlook 2010 after you apply the hotfix package. If you apply the hotfix package after you start Outlook 2010, the issue will still occur. To work around this issue, you must create a new profile in Outlook 2010.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.