[SigmaTel STAC9227, Green Headphone Out, Front] Sound only after plugging in connector in the rear then reconnecting front

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My onboard front audio (headphones) only starts working after plugging in some connector in the rear jacks, then reconnecting the front audio. I can then plug out the rear connector as headphones started working. Doesn't happen in Windows. These are my sound devices:

== Onboard SigmaTel/IDT STAC9227 audio codec ==

00:1b.0 Audio device: Intel Corporation N10/ICH 7 Family High Definition Audio Controller (rev 01)
    Subsystem: Intel Corporation Device a201
    Kernel driver in use: HDA Intel
    Kernel modules: snd-hda-intel

== Offboard Genius SM-Live Value 5.1 sound card ==

04:00.0 Multimedia audio controller: C-Media Electronics Inc CM8738 (rev 10)
    Subsystem: C-Media Electronics Inc CMI8738/C3DX PCI Audio Device
    Kernel driver in use: C-Media PCI
    Kernel modules: snd-cmipci

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: alsa-base 1.0.24+dfsg-0ubuntu1
ProcVersionSignature: Ubuntu 2.6.38-10.46-generic 2.6.38.7
Uname: Linux 2.6.38-10-generic i686
AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.23.
Architecture: i386
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC1: renato 1547 F.... pulseaudio
 /dev/snd/pcmC1D0p: renato 1547 F...m pulseaudio
 /dev/snd/controlC0: renato 1547 F.... pulseaudio
Card0.Amixer.info:
 Card hw:0 'CMI8738'/'C-Media CMI8738 (model 55) at 0x1100, irq 21'
   Mixer name : 'CMedia PCI'
   Components : ''
   Controls : 41
   Simple ctrls : 22
Card1.Amixer.info:
 Card hw:1 'Intel'/'HDA Intel at 0x90200000 irq 44'
   Mixer name : 'SigmaTel STAC9227'
   Components : 'HDA:83847618,8086a201,00100201'
   Controls : 26
   Simple ctrls : 17
CurrentDmesg:
 [ 30.040069] eth0: no IPv6 routers present
 [ 30.160907] Adding 1048572k swap on /swap. Priority:-1 extents:806 across:1262728k
Date: Sat Jul 30 20:47:22 2011
PackageArchitecture: all
ProcEnviron:
 LANGUAGE=pt_BR:en
 LANG=pt_BR.UTF-8
 SHELL=/bin/bash
SourcePackage: alsa-driver
Symptom: audio
Symptom_AlsaPlaybackTest: ALSA playback test through plughw:Intel successful
Symptom_Card: Áudio interno - HDA Intel
Symptom_Jack: Green Headphone Out, Front
Symptom_PulsePlaybackTest: PulseAudio playback test successful
Symptom_Type: None of the above
Title: [, SigmaTel STAC9227, Green Headphone Out, Front] Playback problem
UpgradeStatus: Upgraded to natty on 2011-06-19 (41 days ago)
dmi.bios.date: 11/07/2007
dmi.bios.vendor: Intel Corp.
dmi.bios.version: TS94610J.86A.0087.2007.1107.1049
dmi.board.asset.tag: Base Board Asset Tag
dmi.board.name: D946GZIS
dmi.board.vendor: Intel Corporation
dmi.board.version: AAD66165-301
dmi.chassis.type: 2
dmi.modalias: dmi:bvnIntelCorp.:bvrTS94610J.86A.0087.2007.1107.1049:bd11/07/2007:svn:pn:pvr:rvnIntelCorporation:rnD946GZIS:rvrAAD66165-301:cvn:ct2:cvr: