MXC051, SigmaTel STAC9200, Speaker, Internal Playback problem

I can hear the bell of login screen but once in my session there is no sound coming from the speakers.
In the sound panel I can only select SPDIF output but when I plug headphones, the headphones output shows in the list.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: alsa-base 1.0.25+dfsg-0ubuntu1
ProcVersionSignature: Ubuntu 3.2.0-22.35-generic-pae 3.2.14
Uname: Linux 3.2.0-22-generic-pae i686
AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.24.
ApportVersion: 2.0.1-0ubuntu1
Architecture: i386
ArecordDevices:
 **** List of CAPTURE Hardware Devices ****
 card 0: Intel [HDA Intel], device 0: STAC92xx Analog [STAC92xx Analog]
   Subdevices: 1/1
   Subdevice #0: subdevice #0
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: david 3604 F.... pulseaudio
                      david 3959 F.... alsamixer
Card0.Amixer.info:
 Card hw:0 'Intel'/'HDA Intel at 0xdfebc000 irq 44'
   Mixer name : 'SigmaTel STAC9200'
   Components : 'HDA:83847690,102801b5,00102201 HDA:14f12bfa,14f100c3,00090000'
   Controls : 13
   Simple ctrls : 6
CurrentDmesg:
 [ 23.198295] init: plymouth-upstart-bridge main process (577) killed by TERM signal
 [ 31.770654] Bluetooth: HIDP (Human Interface Emulation) ver 1.2
 [ 33.216022] eth1: no IPv6 routers present
 [ 184.425328] show_signal_msg: 36 callbacks suppressed
 [ 184.425336] compiz[1642]: segfault at 11 ip b4c9792a sp bfe7588c error 4 in libanimation.so[b4c53000+75000]
Date: Tue Apr 17 02:37:30 2012
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Beta i386 (20120301)
PackageArchitecture: all
ProcEnviron:
 LANGUAGE=es_AR:es
 TERM=xterm
 PATH=(custom, no user)
 LANG=es_AR.UTF-8
 SHELL=/bin/bash
SourcePackage: alsa-driver
Symptom: audio
Symptom_AlsaPlaybackTest: ALSA playback test through plughw:Intel successful
Symptom_Card: Audio incluido - HDA Intel
Symptom_Jack: Speaker, Internal
Symptom_PulsePlaybackTest: PulseAudio playback test successful
Symptom_Type: Only some of outputs are working
Title: [MXC051, SigmaTel STAC9200, Speaker, Internal] Playback problem
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 03/13/2006
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A04
dmi.board.name: 0HC416
dmi.board.vendor: Dell Inc.
dmi.chassis.type: 8
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvrA04:bd03/13/2006:svnDellInc.:pnMXC051:pvr:rvnDellInc.:rn0HC416:rvr:cvnDellInc.:ct8:cvr:
dmi.product.name: MXC051
dmi.sys.vendor: Dell Inc.