I have a Vizio P50 HDM where the picture will not come on but I can hear the sound. The unit is hooked up to a cable box and then to a DVD player. It has worked fine hooked up this way for 1 1/2 yrs and now, nothing. I unplugged it and plugged it back in, still no picture, just sound. could it be a weak signal or maybe a settting is wrong? Could it be the remote settings?