The audio on my macbook suddenly stopped working. When I click on the audio adjuster, it won't even let me change the level (the little circle is white now, not blue). But when I plug in headphones or an external speaker, everything works fine. I can once again adjust the audio and get sound There was a red light eminating from the audio out jack for a while (last couple of days) but today, there is no longer a red light. Still no audio from the speakers. Any help appreciated.