I have a Logitech z-680 speaker system, and I have my dvd player hooked to it (via optical), my pc hooked to it (via coax), and my wii hooked to it (via RCA to 1/8" adapter). When the coax cable is hooked to my pc (which plugs into a circuit board which connects via small ribbon cable to my systemboard, I get a white line moving slowly up the screen when on Video 1 (the input my Wii is on. When the coax cable is hooked to the dvd player, no problems, just from the pc. I'm wondering if there's some sort of noise coming from my pc or what could be causing this. I have to unplug the coax cable when I want to play the wii (if I want an excellent picture). Any thoughts?