My friend is having a problem with an iPhone 4 (not yet updated to iOS 5).
Most apps and the ring tone will make noise via headphones but not via speaker. iTunes and at least one other app will play sounds via the speaker, however.
What could cause some apps to become muted on the speaker but not others? No settings were deliberately changed, but there are young children who use the device and could have set something. Is there a simple way to reset the phone and preserve apps and data but make the speaker work again in all apps?