You install the update that is mentioned in Knowledge Base (KB) article 976985 or a later version of the update. When you change a distribution group name, the distribution group may not work for Microsoft Office Communicator 2007 R2 clients. Additionally, the distribution group displays incorrect information in Microsoft Office Communicator 2007 R2. For example, the distribution group display icon is a user icon instead of a distribution group icon.
This problem occurs because Office Communicator 2007 R2 tries to read the group type from the compact delta address book file. However, the group type is not in the compact delta address book file.
To resolve this problem, install the following update rollup:
2028888 Description of the cumulative update package for Communicator 2007 R2: July 2010
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
For more information about KB article 976985, click the following article number:
976985 Some user accounts are locked out when you use Office Communicator 2007 R2