I used to have this problem when I played blurays in PowerDVD when it was launched from within Media Center. If I opened PowerDVD from outside of Media Center and played a movie, it was OK. What I found out in my case was the setting for the display type I had selected when setting up Media Center. At the time, I had a rear projection HDTV so I had chosen TV. I found a fix that said to change the display to Flat Panel or Projector. It worked for me.
