Is the channel a 5.1 signal? Not all channels have 5.1 audio available, and will default to a 2.1 (Two fronts and subwoofer) when channels are broadcast in Stereo.
I just got a new HT BD1250 home theater system and the front speakers and the sub-woofer is all that's working now. I have a 55" samsung TV and it is plugged into the optical audio. It worked just fine yesterday, and today when I turned it on no surround sound. Any thoughts?