DVD decryption problems

[reloop]

Hi everybody,
I recently bought a DVD RW to backup my DVD's but with the decryption of some of my DVD's i have some problems.
For decryption i have tried DVD Decrypter and Smartripper and both this programs are unable to unlock certain files of the DVD (vob files i believe).
With some of this DVD disks my DVD rom could not even read it and a error like "uncknown format" shows up.
The DVD's wich are having this problems all work fine in my standalone DVD player.
Help me out please.

[macleod]

check the underside of the DVD for distortions. If a DVD has been out in the sun or seomething, they may play fine on a standalone, but wont on a pc dvd player/burner.

I've had 2-3 movies that have done that. Yet another reason to back up movies to DVD-R