So now, when I start horizons I get root element missing on ISE.
That’s odd. “Error: Root element is missing” indicates a corrupted config file. What does the first two lines of your Custom.x.x.binds file look like?
Take a look at this thread:
http://developer.tobii.com/community/forums/topic/infinite-screen-extension-step-by-step-troubleshooting/#post-4393
If that doesn’t fix your problems then please contact the Tobii support.