When you put in the DVD that came with the magazine and run a check, how long does it take? is it coming back almost straight away or does it take a few minutes?
It should take a little while to check a DVD against it's MD5 (as it will if you manually create an MD5 file in the way I mentioned in the previous post), and what I think is happenning is that the check is failing, but it's returning the wrong error code so the application thinks it's passed. If this happens, the check will return a result quickly (more-or-less straight away).
The error happens when the application checks the medium. The burned disk, on the other hand, gets passed this point (the application was designed to check burned disks) and fails the check at a later stage (when it looks for the MD5 file) which returns the correct error code, and so displays an error message.
I should point out that I'm not an expert on this application's code. However, the amount of time it's taking to check will tell you if it's actually doing an MD5 check or not. If it's taking a while to check the pressed DVD and returning a correct result, then ignore the above, the problem must be something else.