I have been burning a few rented videos and sometimes get one that will not burn as it is dirty, scratched, or cracked.
You can hardly go back to the store and say "I want another one as I could not copy this one !"
I have had a bit of success cleaning them with isopropol alcohol.
I usually use DVDDecrypter and that craps out after 30 re-try's.
I have had a bit of success with Ripit4me as that seems to rip the file ignoring some bad areas.
What do you think ?