It sounds like you've messed with the options and switched something 'off' or 'on' by mistake...? I doubt it has anything to do with your TV not being able to handle the sound through HDMI- if it has a legit HDMI port all would be fine in that department.
One other option would be to exchange your current disk for another one. The disk could be a little defective and that would explain only the cutscenes having no sound.