I am not sure if my situation is similar to yours but when I got my 40 inch, 650 Samsung tv I tried my cable box with the HDMI connection. It didn't work. Only the component cables worked. Since my cable box was rented, a cable technician looked at it and said that the box was faulty. He replaced it with a new box and now the HDMI works for me.
I can't get my TV to display cable through HDMI. It works fine from the wall jack to TV but not through the cable box. I have also tried a scientific Atlanta box. 4 months and I decided to check here.
I tried switching HDMI cables too. What should I do?