This could happen if your cable company uses Motorola or Pace brand cable boxes.
- Turn off the tv and the cable box.
- Then turn tv back on.
- Select the HDMI source by pressing the AV+ on the remote.
- Turn the cable box on.
If this does not work you will need to return the box to the cable company. They will either need to give you one that is from another manufacturer or disable the HDCP for that box.