Hi John,
Thank you for the additional information. DOS is definitely the best way to go as far as testing the most memory possible since the footprint of the untestable memory is so small. So it is very peculiar that we are not detecting a failure. Out of curiosity, are all of the memory sticks exhibiting this behavior the same brand/type/size? Would it be possible to upload the logs from the failed tests as well as the successful tests so that I may look at the differences? If you do not want to upload them here, please feel free to attach them to an email to support@pc-doctor.com.
Thanks,
Channing