could be a problem with the ripping, I've never used dvdbackup, I always use mactheripper,
soI'm not sure of the difference, if clicking play movie doesn't work, there should be files called something like menu01.vob etc, if not, it may be that it wasn't ripped correctly, there should be some other files as well, like white docs, they're small files that tell the menu how to work and such, if they're missing, thats probably part of it. if you can, I suggest using mactheripper and rip it again.