I can't speak for Rocky 3, but I just loaded Shrek in my copy of DVD Shrink 3.0 Beta 3 and it analysed it without any problems.
You might find the earlier version of DVD Shrink had some bugs that needed ironing out, particular with certain drives.
Jump onto the site at
www.dvdshrink.org and download the latest version, and see how you go.
If that is not successful then you might have some sort of device conflict but I'm no expert
