So you’ve installed Linux (Ubuntu in my case), added your prefered dvd player (if not already installed), and installed libdvdcss.  Great, now you can watch your film.  But your new dvd wont play.

Check that you have set the region for you dvd drive as this was my problem.  I’ve never had this problem before and it was only by chance I tried this solution.  The program to do it was regionset and you can learn more about it at this web page.