Recent Lync Control Panel Issue (AdminUIHost AppCrash)

March 2013 Update:  A fix for this issue is now available.  See A Fix for the Lync 2010 Control Panel Crash Issue on VMWare for more information.

I have experienced an issue recently with the Lync Control Panel crashing on several Lync servers. It appears the problem is caused by a recent Silverlight 5 update, but may or may not surface on all Lync servers. The issue is being investigated, but in the meantime, if you are experiencing this issue there are two easy workarounds:

  1. Launch the Lync Control Panel from a web browser using the pool FQDN. This will take the form: https://<pool_FQDN>/CSCP.  Don’t forget the “s” or a HTTP 403 forbidden will be returned.
  2. Uninstall Silverlight 5 and re-install Silverlight 4. You can download Version 4 of Silverlight here:

The issue manifests itself if you launch the Lync Control Panel from the Windows Programs menu which uses an IIS component called AdminUIHost.exe.  After a period of between 0 and 5 minutes, you will get the following error:


The culprit appears to be a recent Silverlight 5.1.10411.0 update (combined with using the AdminUIHost.exe component):


June 25, 2012 Update

Microsoft is aware of this issue. It appears to be a Silverlight 5 issue when running on VMWare (version unknown).  There is no ETA on a fix and the recommended solution for now is to rollback to Silverlight 4.x.

Here is a thread on a VMWare forum that discusses the Silverlight 5 issue:

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