I'm sorry to hear that you're having this issue. I'll see if I can assist.
First, make sure that you're using the HDMI-2 input, as it's marked HDMI/DVI and is for this purpose.
Then, on Page 17 of the manual, it explains how to Edit the Input Source Name. You'll want to change the name of your input from "----" to "PC".
To do that (in case you don't have the manual nearby):
Press MENU > INPUT > EDIT NAME (and then choose PC and ENTER). The PC should be in the resolution of 1920x1080 @60hz.
Editing the name of the input will enable the audio inputs for the HDMI-2 port.
Does that work?
I have a Samsung LN32A550P3FXZA that I'm trying to connect to my 2009 MacBook Pro 15". I have the DVI-HDMI cable and the Red/White RCA cable for audio. I can get video from the Mac to the TV, but I can't get audio. I have the HDMI cable in the HDMI3 port on the TV (on the side, not the back). I have the red and white cables in the ports just below that HDMI port and I still can't get any sound. Does anyone have any suggestions?