Article ID: 2882812 - View products that this article applies to.
Consider the following scenario:
Note The proxy authentication is not required, and you do not receive a 407 error.
If you input your credentials when prompted and then select the check box to save the credentials, the dialog box will disappear. The dialog box will disappear even if the credentials are invalid.
To resolve this issue, install the following update:
(http://support.microsoft.com/kb/2825630/ )Description of the Lync 2013 update: September 20, 2013