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.
Member RevoMaxx is quickly moving up the ranks of Acer Community. He joined us in September and is already making a difference. It's great to see new members like him make a difference only after a few months. Thanks RevoMaxx!