Microphone not working, even after replacement

I have an iphone 3g that I have been working on for a friend. When I received the phone it had many problems, and a non functional mic was one of them. I noticed a small tear on the ribbon cable of the mic, and assumed that was it. I replaced the whole dock connector (along with the home button, camera, and back cover). I forgot to test the mic before I gave it back, and it is still not working. I have the iphone apart now and I can't see anything wrong physically with it. The mic ribbon cable looks good, and connector 4 is firmly in place. Everything works but the mic. I've also tried restoring the phone several times. I really don't know where to go from here.