Symptoms
Assume that you try to open a Right Management Service (RMS)-protected email message that has a large attachment. In this situation, Outlook 2010 stops responding.
Note The email message will open eventually after 4 to 5 minutes.Status
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
Resolution
To resolve this issue, install the following update package:
2516475 Description of the Office 2010 hotfix package (Mso-x-none.msp): April 26, 2011