I'm not sure what this error is, but DVD Shrink is way out of date and many DVDs have a copy protection that Shrink cannot decrypt. This may be the error. I use DVDfab Decrypter, from
www.dvdidle.com (it's the free version) to remove the copy protection, then I open up DVD Shrink and use the "Open Files" button and select the source of the ripped disc.