Same problem-- built in speakers don't work!
Exact same problem, except that I can't get the built-in speakers to work by wiggling the headphone cord. I can listen to sound through my headphones, but not through the speakers. In the system preference there is no option under "output" for built-in speakers, only the option to choose headphones. It is really odd. You simply wiggled a cord? I still have the red internal light. Did you recently install/uninstall anything? Any suggestions?