We're having issues with the sound on our Virgin service. There's crackles and wowing on the sound; it's much more pronounced on HD TV, but on SD there's some syncing issues with the picture. I've tried resetting, and switching off the Dolby, but no good.
Try a new good quality HDMI cable and also try a different HDMI port on the TV.
-------------------- Services: HD TV on VIP (+ Sky Sports & Movies & BT sport), x3 V6 boxes (1 wired 2 WiFi,) SH2 in modem mode with Airport Extreme Router. On VIVID200, Talk Anytime Phone, x2 Mobile SIM only iPhones.