[ICH4 - Intel ICH6] pulseaudio no sound in gnome after 10.4 upgrade

Binary package hint: pulseaudio

System is a Dell D610 PentiumM 1.87.
After upgrading to 10.4 sound stopped working at all, drivers are correctly loaded, no error messages in dmesg, all levels in alsamixer are set to high and sp/dif output is disabled. I cannot check if sp/dif is working since it is only available through the docking station of my laptop.
Neither the headphones nor the internal speakers work.
Sound works correctly in WindowsXP

After further testing it appears that sound is working on the system but not through pulseaudio

ermanno@ermanno-laptop:~$ aplay -D front /usr/share/sounds/purple/login.wav
Playing WAVE '/usr/share/sounds/purple/login.wav' : Signed 16 bit Little Endian, Rate 22050 Hz, Stereo
Sound is played correctly

ermanno@ermanno-laptop:~$ aplay -D pulse /usr/share/sounds/purple/login.wav
Playing WAVE '/usr/share/sounds/purple/login.wav' : Signed 16 bit Little Endian, Rate 22050 Hz, Stereo
NO SOUND

ermanno@ermanno-laptop:~$ aplay -L
pulse
    Playback/recording through the PulseAudio sound server
front:CARD=ICH6,DEV=0
    Intel ICH6, Intel ICH6
    Front speakers
surround40:CARD=ICH6,DEV=0
    Intel ICH6, Intel ICH6
    4.0 Surround output to Front and Rear speakers
surround41:CARD=ICH6,DEV=0
    Intel ICH6, Intel ICH6
    4.1 Surround output to Front, Rear and Subwoofer speakers
surround50:CARD=ICH6,DEV=0
    Intel ICH6, Intel ICH6
    5.0 Surround output to Front, Center and Rear speakers
surround51:CARD=ICH6,DEV=0
    Intel ICH6, Intel ICH6
    5.1 Surround output to Front, Center, Rear and Subwoofer speakers
iec958:CARD=ICH6,DEV=0
    Intel ICH6, Intel ICH6 - IEC958
    IEC958 (S/PDIF) Digital Audio Output

ProblemType: Bug
DistroRelease: Ubuntu 10.04
Package: alsa-base 1.0.22.1+dfsg-0ubuntu3
ProcVersionSignature: Ubuntu 2.6.32-18.27-generic 2.6.32.10+drm33.1
Uname: Linux 2.6.32-18-generic i686
AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.21.
Architecture: i386
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: ermanno 1254 F.... pulseaudio
Card0.Amixer.info:
 Card hw:0 'ICH6'/'Intel ICH6 with STAC9750,51 at irq 16'
   Mixer name : 'SigmaTel STAC9750,51'
   Components : 'AC97a:83847650'
   Controls : 38
   Simple ctrls : 24
Date: Thu Apr 1 15:08:35 2010
InstallationMedia: Ubuntu 9.10 "Karmic Koala" - Release i386 (20091028.5)
PackageArchitecture: all
ProcEnviron:
 LANG=en_US.utf8
 SHELL=/bin/bash
SelectedCard: 0 ICH6 ICH4 - Intel ICH6
SourcePackage: alsa-driver
Symptom: audio
Title: [ICH4 - Intel ICH6] ALSA test tone not correctly played back
dmi.bios.date: 10/02/2005
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A06
dmi.board.name: 0XD762
dmi.board.vendor: Dell Inc.
dmi.chassis.type: 8
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvrA06:bd10/02/2005:svnDellInc.:pnLatitudeD610:pvr:rvnDellInc.:rn0XD762:rvr:cvnDellInc.:ct8:cvr:
dmi.product.name: Latitude D610
dmi.sys.vendor: Dell Inc.