This issue occurs when the application sharing session calculates whether Microsoft Lync 2013 should automatically re-join the session. During this calculation, the session traces some parameters. This issue occurs in this trace statement.
The conference may be disconnected because of media time-out or network problems.
The string that is described here is displayed as "!%bool!". In the correct format, the string should be "%!bool!".
To resolve this issue, install the following update:
2899507 November 11, 2014 update for Lync 2013 (KB2899507)