Assume that the UserData field in the AbUserEntry table of the RTC database in a Microsoft Lync Server 2010 environment is corrupted. In this situation, the Address Book service does not synchronize user information between the Address Book files and the user database. Therefore, the user information in the Address Book files is not up to date.
To resolve this issue, install the following cumulative update:
2670352 Description of the cumulative update for Lync Server 2010: February 2012