Report "I have an HG216D Hanns_G 21inch monitor and the screen keeps getting big horizontal white lines across the screen. They sometimes go completely dark, but when i've kept the monitor on for some time it starts working (with an area of the screen showing some kind of discoloration). Its not the video card or the cable tested those 2 already. Any ideas on what it could be? THanks for any help you can provide"