There is obviously a mismatch between region codes. Since you state that your computer is set to read US/Canada region, my first thought is that the DVD is for another region. Try playing the problem DVD on your TV's DVD player. And try to play a known US/Canada DVD in your computer.
Own a Predator Laptop? Then I bet you have learned a thing or two from beststevie. He has been helping out in this forum for quite a while and it's about time we recognized him for it. Thanks beststevie!