CentOS - Sep 2013 - Pulseaudio deson't start automatically in gnome desktop

Hi all,

 I have a strange problem in my CentOS 6.4 (fully patched)
workstation: I need to start pulseaudio maunally if I would like to
use/listen sound ... And I don't understand why.

 These are a list of packages related to sound system installed in
this workstation:

alsa-lib-1.0.22-3.el6.x86_64
alsa-plugins-pulseaudio-1.0.21-3.el6.x86_64
alsa-utils-1.0.22-5.el6.x86_64
gstreamer-0.10.29-1.el6.x86_64
gstreamer-plugins-bad-free-0.10.19-2.el6.x86_64
gstreamer-plugins-base-0.10.29-2.el6.x86_64
gstreamer-plugins-good-0.10.23-1.el6.x86_64
gstreamer-tools-0.10.29-1.el6.x86_64
gnome-media-2.29.91-6.el6.x86_64
gnome-media-libs-2.29.91-6.el6.x86_64
pulseaudio-0.9.21-14.el6_3.x86_64
pulseaudio-gdm-hooks-0.9.21-14.el6_3.x86_64
pulseaudio-libs-0.9.21-14.el6_3.x86_64
pulseaudio-libs-glib2-0.9.21-14.el6_3.x86_64
pulseaudio-utils-0.9.21-14.el6_3.x86_64

 Do I need to install something else?? Any idea??

 Thanks.