When executing McxStandalone.msi* (for Lync Mobile) directly from within the browser immediately after download, you may be greeted with the following message:
Microsoft Lync Server 2010, Mobility Service Setup
Failed to open XML file, system error: -2147024786**
[ OK ]
This unexpected error pops up on a Lync Server 2010 Front-End Server running on Windows Server 2008 R2 SP1. This can happen independent of the installed language version for the former, the latter or both. The regional locale settings also do not play a role.
To resolve this issue, start a command-prompt with elevated privileges and execute McxStandalone.msi (follow by Bootstrapper.exe in the %ProgramFiles%\Microsoft Lync Server 2010\Deployment) straight from the directory.
* Microsoft Lync Server 2010 Mobility Service and Microsoft Lync Server 2010 Autodiscover Service (link)
** Fehler beim Öffnen von XML-Datei, Systemfehler: -2147024786