I just got a DYNEX 1080p LCD VT for a gift and I'm having trouble setting it up to my first gen white xbox 360. I switched it from TV to HDTV on the av cable and i plugged in the red blue and green wires where they're suppose to go but for some reason the sound wont work. I'm also trying to setup my turtle beach x11 headset but that can wait till i get the sound to come out pf the TV at least first. Am i doing something wrong or missing something. If anyone can help it would be greatly appreciated.