This prog seems pretty decent and fast but it also appears to be very picky on the files it accepts. I too have been getting a number of error messages regarding DVD compliancy.
Also to this point, while I can put something transcoded with DVD2One or DVD95Copy into it to create a menu, the reverse is not true. If I want to "shrink" something created with DVD Author, neither DVD2One nor DVD95Copy will accept it.
I'm assuming it's due to the fact that DVD2One is fussy about files that were altered by another prog, other than a ripper, of course.