New quad-core i5, replacing a 4-yr old macbook and 7-yr old Dell I get the audio chime at bootup, but then the audio cuts out permanently at some point. For example, I heard the skype start-up noise, but then all audio disappears. No itunes, no youtube, no sound effects, nothing. If i plug in headphones, I hear just fine. Rebooting doesn't bring it the soundback (except for the startup noise). I googled, but haven't found anything fitting yet. Suggestions?