A Microsoft Lync 2010 client cannot download the address book file by using a File URL format.
Note The File URL format is also known as a Universal Naming Convention (UNC) path.
This issue occurs because the early versions of Lync clients do not support UNC download paths.
To resolve this issue, install the following cumulative update:
2571543 Description of the cumulative update package for Lync 2010: July 2011
For more information about the new address book features in Lync Server 2010, visit the following Microsoft website:
General information about the new address book features in Lync Server 2010For more information about the address book file download service in Office Communications Server 2007 R2, visit the following Microsoft website: