I also had trouble with my internal speakers after playing music to my friend's stereo.
-When computer turns on, I can hear the computer start
-After the computer is on, speakers won't work
-Red light was on when playing iTunes, QuickTime Player, etc.
-Headphones work when plugged in
(The computer thinks that headphones / or other external jacks are in, even though nothing connected)
I went to the nearest Apple Retail Store for an appointment, and this is what I observed:
Step 1: Turn off computer, then turn it back on.
Step 2: After you hear the computer turn on, immediately press (option
command+RP)
Step 3: After pressing all the keys, you will hear the computer start up twice, LET GO.
Result: The computer started, then speakers worked properly.
Note: If that doesn't work press (control
command+RP)
What I learned from this:
-Buy an AirPort for you stereo
-Make a Playlist for your iPod to connect to the stereo so that you can forget about it
-Never connect my MacBook to someone else's speakers
-Must have: 3 year AppleCare
-Call the AppleCare 1-800 number, so that you don't have to drive 50 miles to the nearest AppleStore
-Be NICE to the Apple Store employee (Even though they are arrogant and snoody, it's not your fault their life *****!)
Hope this helps! Good luck!