I think it all about your settings or there is a mechanical problem with your TV. You need to open your menu, then audio and proceed to advanced audio to access the SRS Trusound HD. This function will automatically adjust the volume levels for satellites. You can as well press the volume push button on the remote control to check for sound.
I have the same TV. But it's not about the volume control it is about the volume you had it set at on its last setting. I watch TV, Internet, Netflix and others, and they all seem to have their own volume settings.