An useful review

Hello.Last airbender problems - I'm not getting anything from decypter, dvdfab or shrink. The files are blank-- duration 00.00 for each and file size reads as 0.01. dvdFab rips in 10 seconds and files are uesless. shrink gives an error message "invalid DVD navigational structure." This has never happened before. Unfortunately, I don't have the technical skill as most people I see posting here. However, I have always been able to backup movies. Does anyone have thoughts about how to help? Thanks in advance!