iTouch viewing YouTube via Forefront TMG

[altecsole]

I'm trying to setup an iTouch to access YouTube videos via our Forefront TMG. I can browse YouTube, but I can't view any videos. I get an message saying "You are not authorised to open this file". Looking in the Forefront logs there are anonymous requests being blocked to googlevideo.com, youtube.com and ytimg.com. Allowing anonymous requests to these sites result in a different message; "The server is not correctly configured".

 

I don't want to allow anonymous request to YouTube, as we currently block it for pupils. This request has come from a media teacher who has some County supplied iTouch devices for exploring their use in education. Any advice gratefully received.