Macbook loss of sound

I had exactly the same problem and the thought of having to do all those re-installs scared me, quite frankly, so I went for the gentle prodding with a toothpick option.

That didn't work - So I got a set of headphones and tried inserting and removing the jack a few times. This did nothing. I then tried with the same jack but as I inserted it, I applied downward pressure to the rubber moulding of the jack, so in effect aiming the pin of the jack at the upper, inside section of the jack socket to try poking at whatever connection may be stuck! I repeated this many times - slowly applying pressure to the rubber moulding in all directions (imagine a clock face) and when I removed it each time, I waited for the red light tome come back, which it always did.

Until it finally worked!

I should point out that after several failed attempts and the re-install option looming - I may have got a bit over zealous with the pressure I was applying and was probably lucky I didn't break the jack and leave the pin in the socket!....Be careful and good luck!