I have a 2 year old Digi+ board which has been working perfectly with my old Panasonic SC BT230 home theater using optical lead. Had to replace the home theater and bought a Panasonic SC BTT405 system. However, I can't get any sound using the optical cable, although HDMI audio works fine but obviously is just stereo, not 5.1 which is what I want. If I can't get optical to work then there is no point using the Digi+ board at all. Any ideas?