problem burning.mkv to dvd

Hi I’ve been following this guide (http://www.matroska.org/technical/guides/dvd/DVDSanta/index.html) to burning .mkv to dvd but have a problem. When I open the mkv file to be burned I get the message “Unsupported video stream” & then “Unable to open the video file of” ....“720p.hdtv.x264-bia.mkv”
I don’t know why. I’ve already checked that I can play the mkv on windows media player (v.11).

I’ve looked for matroskadiag.exe but don’t have this installed with dvdsanta and can’t find this on the matorska website, or elsewhere. Does anyone know where I can get this or otherwise provide any assistance to getting this file burned to dvd?

Thanks

anyone?