it sounds like a protection issue
okay, first off DVD Shrink has not been updated for a while thus it will not be able to handle all of the newer movies,because of this u have to rip the movie 2 HDD first before u shrink it or u can use AnyDVD while running shrink
0.What movie are u trying to back up?
1.Are u using AnyDVD while using shrink?
2.Did u rip the movie first to your HDD?
You can break the protection of all the new movies that have come out. all u need is the latest verion of either AnyDVD or dvdFab decrypter.
Here is link to DVDFab decrypter
http://www.dvdidle.com/free.htm