iPhone 4 Temporarily Lost Sound

My wifes phone did the same thing. My kids noticed it playing doodle jump. Rebooted and sound came beck.

I had the same problem. But my phone would also not ring. I was on the phone with Apple Care for a couple of hours and nothing helped at first. We restored, restarted and what seemed like a bazillion other things. We finally got it back by making a phone call and pressing the speaker phone button then turning the speaker phone off again. But it happened again while I was on the phone and we did the same fix. Finally he said bring it back to an Apple store, which I did. Apple ran a couple of diagnostics and could not find anything. They exchanged it, no problem. Still don't know what the problem was.

Are you on 4.0.1? This was a known (and reportedly fixed) defect in 4.0.

I had the issue but I went to 4.1 beta and skipped 4.0.1 so I don't know for sure. I do know the problem is gone in 4.1 beta 3.

I was using 4.0.1 when it happened to me.

Happened to my first 4 and the "geniuses" told me to restore the phone and set it up as a new device. I tried that and it still lost it's sounds every once and a while. Not sure what the problem was but they reluctantly swapped the phone out and it hasn't done it since. Might go talk to them?

Do you run Skype? I've noticed that hen I have skype running in the background, the volume gets all wierd and quiet.

The defect 'resolution' from Apple on this indicated it was a problem with background audio apps (skype, pandora, etc.) not doing the right thing. Have you downloaded the latest on all those?