Why does the display flick on and off, with no audio interruption?

The TV image flicks on and off with no interruption in audio. It does not have lines or fading. It is just on then off. It does it with the apple box, cable box and blue ray disc. We have tested the following:

1) Connected to an alternate TV with same cable. Same problem.

2) Switched the HDMI cable on both TV A and TV B. Same problem.

3) Switched the cable box. Same problem.

We believe it has to be the receiver. We have updated firmware. Cannot find a solution.