Consider the following scenario:
You configure the User Profile Synchronization service in Microsoft SharePoint Server 2010.
You have an msOnline-UserPrincipleName attribute in the Active Directory domain schema.
You synchronize the user profile.
You create a My Site page for the user profile in SharePoint Server 2010.
In this scenario, some unexpected symptoms occur. For example, the URL of the My Site page is displayed as a cryptic string instead of as a user name.
This issue occurs because the msOnline-UserPrincipalName attribute is a reserved attribute in the Active Directory domain schema.
To resolve this issue, apply the following hotfix:
2475878 Description of the SharePoint Server 2010 Cumulative Update Server Hotfix Package (MOSS server-package): March 3, 2011
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.