Automatic migration. Original reporter: "lindquist"
The System constructor subscribes to the Renderer::EventDisplaySizeChanged of the renderer module, but does not unsubscribe from this during destruction.
If you recreate the system, but use the same "old" renderer, then you end up having multiple subscriptions to this event.
Reported here: http://www.cegui.org.uk/phpBB2/viewtopic.php?t=1527