Hi, I bought a Samsung 60 inch LED HDTV (model UN60H7100AF) in November, 2014 from Costco.com. It's wall mounted and not easy to return. However, I bought the extended warranty. In the past month it has developed a single vertical red line on the screen when it's turned on. I've only owned it for less than 6 months and it was new. Any idea what is causing this?