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.
Please join me in congratulating IronFly who is the first Acer Community Member to achieve the rank of ACE Pathfinder. IronFly has shown a consistent willingness to help others and has worked hard to earn this new Rank. Congrats and Thank You IronFly.