[NFORCE - NVidia nForce2] ALSA test tone not correctly played back

Sound has stopped working after applying updates on an Ubuntu 10.4.1 LTS system.

I expect sound not to stop working after applying these updates or at least that there is a way to make it work again. No changes that I apply to sound preferences make any difference. I also don't know if this is an issue with alsa-driver (unlikely) or pulseaudio.

ProblemType: Bug
DistroRelease: Ubuntu 10.04
Package: alsa-base 1.0.22.1+dfsg-0ubuntu3
ProcVersionSignature: Ubuntu 2.6.32-25.44-generic 2.6.32.21+drm33.7
Uname: Linux 2.6.32-25-generic i686
AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.21.
Architecture: i386
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: sharon 1246 F.... pulseaudio
Card0.Amixer.info:
 Card hw:0 'nForce2'/'NVidia nForce2 with ALC650F at irq 20'
   Mixer name : 'Realtek ALC650F'
   Components : 'AC97a:414c4723'
   Controls : 50
   Simple ctrls : 33
CurrentDmesg:
 [ 27.292015] eth0: no IPv6 routers present
 [ 78.021517] ondemand governor failed, too long transition latency of HW, fallback to performance governor
Date: Fri Oct 15 21:21:48 2010
InstallationMedia: Ubuntu 10.04.1 LTS "Lucid Lynx" - Release i386 (20100816.1)
PackageArchitecture: all
ProcEnviron:
 LANG=nl_NL.utf8
 SHELL=/bin/bash
SelectedCard: 0 nForce2 NFORCE - NVidia nForce2
SourcePackage: alsa-driver
Symptom: audio
Title: [NFORCE - NVidia nForce2] ALSA test tone not correctly played back
dmi.bios.date: 09/17/2003
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: 3.14
dmi.board.name: A7N8X-LA
dmi.board.vendor: ASUSTeK Computer INC.
dmi.board.version: Rev 1.xx
dmi.chassis.asset.tag: Asset-1234567890
dmi.chassis.type: 3
dmi.chassis.vendor: Chassis Manufacture
dmi.chassis.version: Chassis Version
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvr3.14:bd09/17/2003:svnHPPavilion061:pnDQ007A-ABHA350.NL:pvr00,0211RE101EXPLO10:rvnASUSTeKComputerINC.:rnA7N8X-LA:rvrRev1.xx:cvnChassisManufacture:ct3:cvrChassisVersion:
dmi.product.name: DQ007A-ABH A350.NL
dmi.product.version: 00,0211RE101EXPLO10
dmi.sys.vendor: HP Pavilion 061