Oh dear, I'm going to have to admit to having been rather dim here. It finally dawned on me to examine the source disc and it looks like the cat's clawed its way over it...which would explain why the copy ended in the same place every time. Tried copying from another disc and all was well. Duh! Thanks anyway for the quick reply, and to answer your question, I was using Disc Copy and the source was a DVD made from burning a Disc Image file some time ago.