The following event is logged in the Office Communications Server log on a Microsoft Office Communications Server 2007 R2 Group Chat server.
Log Name: Office Communications Server Source: OCS MGC Logged: Date Event ID: 5377 Task Category: (1099) Level: Error Keywords: Classic User: N/A Computer: Computer Name Description: Failed to update the database with AD changes.  String or binary data would be truncated. The statement has been terminated.
This issue occurs if you create a user in the Active Directory directory service who has a distinguished name of more than 256 characters, and then you add this user to a distribution group.
To resolve this issue, install the following cumulative update:
2549044 Update package for the Office Communications Server 2007 R2 Group Chat server: June, 2011
Note After you apply this update,the Group Chat server supports up to 384 characters in the distinguished name.