Invalid DVD Navigation Structure in Shrink ?

[whenevere]

Using DVD Shrink 3.1 to "open disk" a dvd, Shrink gave the error message "invalid DVD navigation structure".

But my dvd can be played by PowerDVD with no problem. The menu is ok in PowerDVD and I can navigate in it. My television DVD player can also play and navigate it with no problem either.

So, what is wrong with DVD Shrink and the dvd disk ?? How can I open it in Shrink ??