Unregistered event could not be registered. Session "&2" is not in the intranet mask "&1".
&1 - The intranet mask registered in the Site Settings.
&2 - The Session ID. Use the "Surrogate" menu item in the administration menu to find the IP address registered for the session.
An unregistered event has been received. The event could not be registered as the session does not come from inside the intranet.
If you think that the session should have been accepted as an internet session you can check the session by using the Surrogate menu item in the administration interface to find out which IP address the web server has registered for the browser.
This can be compared with the value for the Site Setting "intranet mask", also specified in the message.