DVDDecrypter is, in programming terms, depricated; in layman's terms outdated. I also used it recently, but one out of about every 6 or 7 DVD I ripped as ISOs simply would not play.
At the suggestion of another Community Member, I bought DVDFab and have yet to run into another non-payable ISO. You can also simply download the trial version and I I understrand its base functionality - rip/strip - never expires.
I hope you have the same good experience with DVDFab I did and if you choose to continue using DVDDecrypter I hope it works flawlessly for you.