I fiddled about with pulseaudio, I think in my config files. Now i can't play 2 things one after each other from 1 window ton another. E.g. on Rhythmbox when i listen to a song then switch to youtube, youtube won't have any sound, and when i do it the otherway round rhythmbox won't play at all, its playback slider doesn't move.
You can reset your PulseAudio settings following the point 1 of part A of this guide. http://ubuntuforums.org/showthread.php?t=789578