Mac to TV via HDMI cable question

I connect my MacBookPro to my HD Sony Bravia TV via an HDMI cable to watch movies. When watching movies the picture gradually pulses from bright and clear to very dark so we can scarcely see what's happening on the screen.

Does anyone have any idea why this is happening and what I can do to stop it?

Thanks a million.

First thing to try is another HDMI cable assuming the quality of the movie you're watching is not suspect. Since HDMI cables are not inexpensive, make sure you can return it for a refund if the old one should be OK.

Thanks. I will definitely try that. Good advice on the refund front if it doesn't do the trick.