Dvd2one vs toast6

Maybe I’m not the first one to ask but I simply couldn’t find this thread so …
has any one got an idea about why dvd2one would work perfectly but roxio’s toast6 would refuse to burn the dvd ?
I must say I already copied several DVDs but it’s the first time this happens to me … no matter what I do, it won’t burn the DVD … I take it that if I can use dvdback up then dvd2one then it can’t be because of a protection on the DVD can it ?