I can explain why the audio from your TV to the receiver doesn't work. This TV doesn't have audio return channel (ARC), so it can't send audio over HDMI. Here's how to connect your TV in order to get the audio to work: http://support-us.samsung.com/cyber/popup/iframe/pop_troubleshooting_fr.jsp?idx=167818&modelname=LN40C610N1F&modelcode=LN40C610N1FXZA
I have a samsung ln40c610. Just purchased a sony str dh520 receiver. HDMI from receiver to tv does not play any sound from the tv to the speakers. If I connect the cable box to the receiver, and then hdmi to tv I hear the cable sound. But now when I play USB videos from the tv I hear no sound -- its just the cable sound going on, while the usb video plays. If I switch off the cable box, still no sound -- but just video.
Then, all of a sudden (after switching off the tv and receiver, and switching it back on later in the evening) the cable box sound stopped working through the receiver. No idea what's going on, this is so frustrating....