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(Only recently acquired CNM from nephew who was fed up of it not playing YouTube etc., so he's now got an Acer Aspire One & iv'e got the CNM book - lack of YouTube not being an issue for me!)
The "Video Online" package from the downloads page at <http://www.cnmlifestyle.com/> does 'play' YouTube videos.
Have you tried?
Unh.
Yes; I'm watching the YouTube Orchestra from Carnegie Hall right now, 15 minutes into a one hour clip (and using a different computer for typing this!). It certainly isn't even close to normal TV, but it is just about bearable most of the time, as a novelty.
I certainly wouldn't want to rely on the picture as a guide to heart surgery, too many frames get dropped, but for light entertainment it's tolerable.
The trick seems to be to set the 'cache' to the minimum of 1 second, so that the processor has as little work to do as possible - which does of course leave you at very much at the mercy of your internet connection. I suspect the characteristics of individual clips also have an effect.