Problem with audio. No sound when streaming movies online. No problem playing DVD through optic drive or iTunes music and YouTube video. Checked sound devise-Realtek HD and it shows that drive is working and speaker set in default settings.
Check that your flash player is installed correctly. Are you using Google Chrome? I experienced a similar sound issue when streaming YouTube videos via Chrome. It got fixed after a while (self fixed), but I changed temporarily to Firefox and sound was back.