I just got a fisher tv from my sister's boyfriend, so its not brand new, but, its not very old either. Everything went great when I first got it, but then after a couple days, I came home and I couldnt see anything on the TV. I could hear the people talking and background noises, etc. But, all I could see was one thin line of multi-colored light going horizontal across the middle of the screen. What happened and what can I do to fix it? Please help!