Lync Servers & Users gathering task fails with "The following error occurred during the processing of a given gathering: SQL Server Network Interfaces: Error Locating Server/Instance Specified [xFFFFFFFF]."
It seems to happen right when the log says "Starting the process of getting external and federated users from the OCS/Lync Server database"
In the task log you notice it is referencing an old OCS database server that used to have LcsCDR on it.
WORKAROUND
Disconnect from the OCS Pool that the Lync Servers & Users task is referencing and rerun the task.
