while playing a video file using Power DVD 11 I experienced no video output on the screen but audio was working fine. When I went into the settings I noticed that the GPU hardware acceleration was enabled. After unticking that option the video playback was fine and all was well but the video lagged a lot as the CPU was now being used to process the video which was a Blu Ray file. I want to use the GPU hardware acceleration but don't know how to fix the problem. I have all the current drivers and software to accompany my ATI 4870 so its not that, could there be a problem with the Cyber link software ? Need help urgently !