Backup Problem for newbie

[helpallus]

i've been trying to backup pirates of the caribean using clone dvd and anydvd (both latest versions) and i seem to get the same problem every time. when i playback on my home dvd the film judders in places ?? thought it was the player so played it on the pc and the same problem. Cleaned the original DVD and tried again but with same outcome. Has anyone else come across this problem ?? usually towards the end of the film ??

cheers for any help
H