Article ID: 2880167 - View products that this article applies to.
Consider the following scenario:
Unknown username and password
If a user installs Lync 2010 and then installs Lync 2013 on the same computer, the user can sign in to Lync 2013 in the scenario that’s described in the "Symptoms" section. However, if the certificate is deleted from the computer, the user can’t sign in to Lync 2013.
To resolve this issue, install the following update:
(http://support.microsoft.com/kb/2825630/ )Description of the Lync 2013 update 15.0.4535.1510: October 8, 2013
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