I dont think this has anything to do with DRM, its the first time i have heard of a DVD with DRM acting that way-and besides dont DVD's rely on that whole CSS protection thing (or is that part of DRM)? Anyways.. from my experience (what ever that means) working with DVDs and such, such an issue usually occurs if the DVD has not been encoded properly at the burning stage- and yes i get that it works in a an ordinary DVD player but i have had a very similar thing happen to me before. I remember once when i went and burnt a family video onto a DVD it played in the regular lounge room DVD player but on a computer i had to go to special effort to make it play.
ALso you know how you said you cant see anything in the folders, have you anabled the ability to see 'hidden files', because the files may be present but simply not shown.
.....Or why not try 'dvd shrink' on the DVD in question and try to transfer the main video file(s) from the DVD to the HD. Although i wonder how many copyright laws it would break.. along with a CSS decrypter
