Just my tuppence worth of problems.
I think my issue is different from others. I'm using a Lenovo X200 laptop and i couldn't get any sound from youtube. I tried installing a different browser as i think was suggested earlier, no luck. I've now tired to play an mp3 file.
Exaile is playing the track but when i go to System-Hardware-Sound it says 'No application is currently playing or recording audio' ?