Speaker not working on iphone 4

[Presto]

The speaker suddenly stopped working on my iphone 4. I can get sound from the head phone jack, and the ear speaker and the mic works just fine. When a call comes in the phone vibrates but there is no sound. I have made sure the silent switch is not on and when you flip it back and forth the phone vibrates, so that appears to be working properly. I have done a full restore and that did not fix it. The phone has never been dropped and it has not been submerged in water. Any ideas?

[Cer0]

Possbily try: plug headphones in. Open music app. Press play and let music start then press pause. Then unplug the headphones. Worked for me once.

[Presto]

Possbily try: plug headphones in. Open music app. Press play and let music start then press pause. Then unplug the headphones. Worked for me once.

I gave that a try and and still no luck.