It looks like themind.xml, music.xml, inspiration.xml, and globalissues.xml do not have this information in the place expected by the code. Everything works in the sample because the default format is .mp4, which the videplayer urls are, but when you modify the code to point to your own files you may expect the StreamFormat to get set to something else and it isn't.
We'll update those files in the next SDK release, but please edit design.xml as a good example of indicating StreamFormat correctly.
--Kevin