Does your source support 5.1 surround sound, and do you have that option selected in the menu? Not all broadcasts and areas broadcast 5.1, although you should be receiving that properly through Blu-Ray.
Recently bought samsung led8000 with a bd1252 cinema sound.
The sound is playing fine through front speakers and subwooffer via blue ray but nothing through rear speakers. Have a sky hd set up, surely I should be getting some surround sound! All speakers are colour connected properly and the optical digital audio lead fitted . Am using hdmi.. hdmi1/dv1