[H55M-USB3, Realtek ALC889, SPDIF Out, Internal] No sound at all

I use the on-board sound chip of a Gigabyte motherboard connected with optical cable to an amplifier.

Everything worked fine, until February, when an update changed the kernel and the PC stopped giving sound signal! When I returned to the previous kernel (at grub), again everything worked.

So, I suppose something happened by that update

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: alsa-base 1.0.24+dfsg-0ubuntu1
ProcVersionSignature: Ubuntu 2.6.38-8.42-generic-pae 2.6.38.2
Uname: Linux 2.6.38-8-generic-pae i686
NonfreeKernelModules: nvidia
AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.23.
Architecture: i386
AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/by-path', '/dev/snd/controlC1', '/dev/snd/hwC1D0', '/dev/snd/hwC1D1', '/dev/snd/hwC1D2', '/dev/snd/hwC1D3', '/dev/snd/pcmC1D3p', '/dev/snd/pcmC1D7p', '/dev/snd/pcmC1D8p', '/dev/snd/pcmC1D9p', '/dev/snd/controlC0', '/dev/snd/hwC0D2', '/dev/snd/pcmC0D0c', '/dev/snd/pcmC0D0p', '/dev/snd/pcmC0D1c', '/dev/snd/pcmC0D1p', '/dev/snd/pcmC0D2c', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1:
Card0.Amixer.info:
 Card hw:0 'Intel'/'HDA Intel at 0xfbff8000 irq 47'
   Mixer name : 'Realtek ALC889'
   Components : 'HDA:10ec0889,1458a022,00100004'
   Controls : 38
   Simple ctrls : 21
Card1.Amixer.info:
 Card hw:1 'NVidia'/'HDA NVidia at 0xf9ffc000 irq 17'
   Mixer name : 'Nvidia GPU 11 HDMI/DP'
   Components : 'HDA:10de0011,10de0101,00100100'
   Controls : 16
   Simple ctrls : 4
Date: Wed May 4 02:26:52 2011
InstallationMedia: Ubuntu 10.10 "Maverick Meerkat" - Release i386 (20101007)
PackageArchitecture: all
ProcEnviron:
 LANGUAGE=el_GR:en
 LANG=el_GR.UTF-8
 SHELL=/bin/bash
SourcePackage: alsa-driver
Symptom: audio
Symptom_AlsaPlaybackTest: ALSA playback test through plughw:Intel failed
Symptom_Card: Internal Audio - HDA Intel
Symptom_DevicesInUse: Error: command ['gksu', '-D', 'Apport', '--', 'fuser', '-v', '/dev/snd/by-path', '/dev/snd/controlC1', '/dev/snd/hwC1D0', '/dev/snd/hwC1D1', '/dev/snd/hwC1D2', '/dev/snd/hwC1D3', '/dev/snd/pcmC1D3p', '/dev/snd/pcmC1D7p', '/dev/snd/pcmC1D8p', '/dev/snd/pcmC1D9p', '/dev/snd/controlC0', '/dev/snd/hwC0D2', '/dev/snd/pcmC0D0c', '/dev/snd/pcmC0D0p', '/dev/snd/pcmC0D1c', '/dev/snd/pcmC0D1p', '/dev/snd/pcmC0D2c', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1:
Symptom_Jack: SPDIF Out, Internal
Symptom_Type: No sound at all
Title: [H55M-USB3, Realtek ALC889, SPDIF Out, Internal] No sound at all
UpgradeStatus: Upgraded to natty on 2011-04-29 (4 days ago)
dmi.bios.date: 11/01/2010
dmi.bios.vendor: Award Software International, Inc.
dmi.bios.version: F11
dmi.board.name: H55M-USB3
dmi.board.vendor: Gigabyte Technology Co., Ltd.
dmi.board.version: x.x
dmi.chassis.type: 3
dmi.chassis.vendor: Gigabyte Technology Co., Ltd.
dmi.modalias: dmi:bvnAwardSoftwareInternational,Inc.:bvrF11:bd11/01/2010:svnGigabyteTechnologyCo.,Ltd.:pnH55M-USB3:pvr:rvnGigabyteTechnologyCo.,Ltd.:rnH55M-USB3:rvrx.x:cvnGigabyteTechnologyCo.,Ltd.:ct3:cvr:
dmi.product.name: H55M-USB3
dmi.sys.vendor: Gigabyte Technology Co., Ltd.