Even 5377 is logged on a Microsoft Lync Server 2010, Group Chat server:
Log Name: Lync Server
Source: LS MGC ENDPOINT
Event ID: 5377
Task Category: (1099)
Computer: <Computer Name>
Failed to update the database with AD changes.  Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding.
Article ID: 2517722 - Last Review: 04/04/2011 19:58:00 - Revision: 1.0