I think it has to do with the frame putting pressure on the cable that connects the LCD to the board of your computer. Do they appear in different places if you hold a different spot when you open your laptop? I think its from when you open your laptop. I had a Toshiba that had the slide lock right in the center. Over time, I developed lines right through my screen in that area. I noticed if I pushed on that spot and kinda wiggled, it make them either worse or better. Does moving your screen, or putting pressure in certain spots make it better or worse?