Pressing [S] causes 'SoundSystem' to stop and restart

When I press [S] to backup, system lags and it shows:

SoundSystem shutting down...
Author: Paul Lamb, www.paulscode.com

Starting up SoundSystem...
Initializing LWJGL OpenAL
(The LWJGL binding of OpenAL. For more information, see http://www.lwjgl.org)
OpenAL initialized

in the cmd window.