Oh! I know the answer to this one!
I laughed as soon as I saw it was Fat Albert you were backing up. I tore my hair out a couple weekends ago doing exactly what you are now.
Fat Albert has a ton of bad sectors on the disc as a form of copy-protection.
So...In DVD Decrypter to into Options and on the I/O tab make sure you checkmark the box "Ignore Read Errors" and set "Software Read Error Retries" to something low...I picked 2.
It will take a l-o-n-g time to read through all those errors, but at the end of the process you should have a working backup.
Oh, only caveat to my advice is that I always keep AnyDVD running so that may have helped with some of the copy protection as well.