Unable to logoff XA 6.5: ICA session displaying “Waiting for System Event Notification Service”

Users cannot log off from a XenApp 6.5 ICA session and the “Waiting for System Event Notification Service” pop-up is displayed.


  • Windows Server 2008 R2
  • Citrix XenApp 6.5
  • Office Communicator 2007 R2


The screen remains unresponsive with the “Waiting for System Event Notification Service” pop-up. On the server user has a Communicator (OCS) running and one of the instances is pegging an entire core resulting in users unable to log off sessions.


As a workaround you can do the following: To log off successfully from the unresponsive sessions, terminate the pegged OCS process.  For a permanent solution you need to apply this fix from Microsoft Cumulative update package for Office Communicator 2007 R2: December 2012.

Original post at the Citrix knowledgebase.

MS Lync documentation

Microsoft Lync Server 2010 communications software offers instant messaging (IM), presence, conferencing, and telephony solutions that can support enterprise-level collaboration requirements.

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