DVD Decrypter I/O error not sure what it means

Using Memorex (Ricoh) DVD writer.
Installed DVD decryptor and when ripping a copy
of Transformers THE Movie - the goofy cartoon show,
it gives me constant I/O error messages and says

Smart Ripper on the other hand gives me no error

Why am I getting these messages ? Should I ginore them?
Does it mean Decrypter cant copy the Transfomer DVD?
Or is it incompatible with my Writer? Or is my writer not able
to read properly ? Then why is smart ripper not giving me error messages?

I also sometimes get read errors with DVD Decrypter from my LiteOn 166s, change to Smartripper and it rips fine. If I then rip from my old Toshiba 8x DVDROM, then DVD Decrypter also reads without a problem.

That tells me there is a difference between DVD Decrpter and Smartripper with reading, as well as readability between my 2 DVDROM units.