Article ID: 980517 - View products that this article applies to.
Consider the following scenario:
Your changes conflict with those made concurrently by another user.
When this issue occurs, the user is deleted in the target source collection. Therefore, you can safely ignore this error message.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
Article ID: 980517 - Last Review: October 6, 2011 - Revision: 4.0