no sound on iphone except incoming calls

Hi all!

pls advise what to do... No sounds on iphone4s, ios5 while typing and locking on and off (already checked in settings and keyboard and lock sounds are "on"), also no sound while playing video and music... However all incoming calls are okay... Never dropped...

Additionally, i noted that while adding and lowering sound through the buttons under mute button, there are no dots under "ringer" word...

Please help to sort this paradox out... Had anyone experienced such a problem? Thanks!