I've got exactly the same problem. I have Dell Inspiron 6400/e1505. I used to stick a headphone jack to get audio but now it became a torture. I think it is because of the headphone switch which cuts the audio. I'm not an expert. I can't repair or replace it. I can get sound when i connect headphones, so the only solution for me is to buy external speakers and connect them to the headphone jack. You will surely have your sound this way.