So I was playing some CoD and got a little bored, so I flicked from the AV channel to Sky and watched TV for a while, and when I switched back.. I wasnt getting any sound at all from the xbox. No game sound and no sound from dashboard browsing (those little pings you get while scrolling). I turned the xbox off and turned it back on, with no luck and made sure the cable was connected up properly, which it is (HDMI cable). Anyone know why its done this and how to fix it?