Copy protection error message but only with LiteOn



This has happened a couple of times to me with AnyDVD and CloneDVD2.
If I try to rip a movie with my LiteOn reader 166s, I get a message saying AnyDVD may not be able to defeat all forms of copy protection on the disc.
However, if I move the disc to my 832s, I don’t get the warning.
Can anyone explain why this may be?
I guess the 166s is just not up to some discs?