You could try installing the latest AnyDVD and restartiong the computer. Then mounting the image, ripping with DVDDecrypter (on the default settings, reset the to default). Then try opening the DVD with DVDShrink.
If that doesnt work the only thing you can do is leave AnyDVD on your computer, get the protected DVD again, and then you should be able to make a copy from that with DVDShrink.
If you want I can explain to you how to make a copy of the main movie only (lose all extras, menus etc.) I think that should still be possible from the image you have.