[Realtek ALC259] ALSA test tone not correctly played back

I'm running wubi-installed Ubuntu Netbook Edition 10.04 on an Asus Eee PC 1015. I initially had no audio out of the box, but fixed it by upgrading to alsa 1.0.23-2. After installing an update from update manager (not sure which update, there were several) a few days ago, I now have no sound from speakers, but there is normal sound from headphones when I plug them in. I have checked sound sliders in sound preferences and alsamixer, nothing is muted. I attempted the fix detailed in Bug #618271 without success.

ProblemType: Bug
DistroRelease: Ubuntu 10.04
Package: alsa-base 1.0.22.1+dfsg-0ubuntu3
ProcVersionSignature: Ubuntu 2.6.32-24.42-generic 2.6.32.15+drm33.5
Uname: Linux 2.6.32-24-generic i686
AlsaVersion:
 Advanced Linux Sound Architecture Driver Version 1.0.23.
 Compiled on Sep 5 2010 for kernel 2.6.32-24-generic (SMP).
AplayDevices:
 **** List of PLAYBACK Hardware Devices ****
 card 0: Intel [HDA Intel], device 0: ALC259 Analog [ALC259 Analog]
   Subdevices: 1/1
   Subdevice #0: subdevice #0
Architecture: i386
ArecordDevices:
 **** List of CAPTURE Hardware Devices ****
 card 0: Intel [HDA Intel], device 0: ALC259 Analog [ALC259 Analog]
   Subdevices: 1/1
   Subdevice #0: subdevice #0
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: ixmasat 1272 F.... pulseaudio
Card0.Amixer.info:
 Card hw:0 'Intel'/'HDA Intel at 0xf7cf8000 irq 29'
   Mixer name : 'Realtek ALC259'
   Components : 'HDA:10ec0269,1043841c,00100100'
   Controls : 11
   Simple ctrls : 7
Date: Mon Sep 6 00:08:13 2010
InstallationMedia: Ubuntu-Netbook 10.04 "Lucid Lynx" - Release i386 (20100429.4)
PackageArchitecture: all
ProcEnviron:
 LANG=en_US.utf8
 SHELL=/bin/bash
SelectedCard: 0 Intel HDA-Intel - HDA Intel
SourcePackage: alsa-driver
Symptom: audio
Title: [Realtek ALC259] ALSA test tone not correctly played back
dmi.bios.date: 04/26/2010
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: 0308
dmi.board.asset.tag: To Be Filled By O.E.M.
dmi.board.name: 1015PE
dmi.board.vendor: ASUSTeK Computer INC.
dmi.board.version: x.xx
dmi.chassis.asset.tag: 0x00000000
dmi.chassis.type: 10
dmi.chassis.vendor: ASUSTeK Computer INC.
dmi.chassis.version: x.x
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvr0308:bd04/26/2010:svnASUSTeKComputerINC.:pn1015PE:pvrx.x:rvnASUSTeKComputerINC.:rn1015PE:rvrx.xx:cvnASUSTeKComputerINC.:ct10:cvrx.x:
dmi.product.name: 1015PE
dmi.product.version: x.x
dmi.sys.vendor: ASUSTeK Computer INC.