Originally Posted by Stephen Warren
Are you using VDPAU output, or Xv? (ppurka who reports the same issue is using Xv).
Can you try adjusting the brightness/contrast/saturation/hue settings in your video application? Alternatively, do this using nvidia-settings after your video player application has started running.
Wow, thanks! Changing contrast setting in mplayer has fixed the problem for the video which originally appeared totally black, as well as for new videos (which appear fine from the start).