Minecraft missing sounds bug

I was break blocks when all the sudden the sound of game, like music and block breaking were all gone.
Is this happening to anyone else

this is the error i found
Client>
Client> SoundSystem shutting down...
Client> Error in class 'SoundSystem'
Client> Command thread did not die!
Client> Ignoring errors... continuing clean-up.
Client> Error in class 'SoundSystem'
Client> Problem during Library.cleanup()!
Client> Ignoring errors... continuing clean-up.
Client> Author: Paul Lamb, www.paulscode.com