I have exactly the same problem with my (old) HT-SL40, which I'm trying to use with a new TV (it also says UNLOCK after selecting DVD, although that seems to work OK).
Also, I'm trying to make the TV connection using a SPDIF Optical cable (which is new to me). The connections clicked nicely into place, and a red light from the TV socket appears at the receiver end of the cable. However, I can get no TV sound from the receiver at all, despite setting the receiver's TV selection to Opt (confirmed by the display) and selecting SPDIF on the TV. Could there be any problem other than the Unlock issue above?
