I'm sorry to hear that you're having trouble.
Have you linked it to a Pandora account?
I've updated the firmware on my PN50B650 HDTV. Pandora is odd, I get various sorts of choices of my Radio Stations, Quick Mix, I even get a screen with a title of something that is playing, but at no time does a peep ever come out of my speakers.
You Tube clips do play properly (though some of them take many minutes to load).