The Registrar service crashes on a Microsoft Lync Server 2010 front-end server after you migrate users from Microsoft Office Communications Server 2007 to Lync Server 2010. Additionally, the following event is logged in the Application log:
This issue occurs because certain user contact entries are incorrect on other users' contacts list. For example, the "user1@" contact entry does not have a domain name. After the migration process, the Registrar service cannot receive information from the corrupted entry when the user logs in. Therefore, the Registrar service crashes.
To resolve this issue, install the following cumulative update:
2571546 Description of the cumulative update for Lync Server 2010: July 2011
To work around this issue, use the Dbimpexp.exe tool to verify that all the contact entries are correct before you perform the migration.