I recently have been experiencing a problem with my picture on my tv. It started out as just a light shadow about a 1/4 inch from the top of the tv. Then that shadow turned black, and now I lost the picture over 3 inches from the top with also and extra inch of another shadow. I cant see the top of peoples heads while watching tv. This is a Magnavox tv and only approx 3 years old. Could this be my cable box? or is my tv going? I do have a digital cable box, I have the optimum service, but I dont have the hd channels. I do not pay for them. what could be the problem?