[YouTube-API] Why some kinds of youtube videos cannot be played in WPF App

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Hi all,
I try to add chromeless player API to WPF app but it seems that there are two kinds of youtube videos cannot be played. I first use ytbplayer.html (as attached) to load youtube player, then use WebBrowser, which is a WPF control, to load the file ytbplayer.html. I found two kinds of videos cannot be played with the solution above.
http://www.youtube.com/watch?v=Nq5Z15hkMoU&feature=BFa&list=FL7hpshIwDvdtNIXQXTrlHcA&lf=plpp_video
http://www.youtube.com/watch?v=CHVhwcOg6y8&feature=BFa&list=FL7hpshIwDvdtNIXQXTrlHcA&lf=plpp_video
Can anyone tell me why? Thanks!

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