Audio not working on Dell E-Port docking station in Jaunty (9.04); was OK in 8.10

I have a Dell Latitude E6400 notebook and a Dell E-Port docking station. Sound through the docking station (i.e. the headphone jack on docking station) was working well in Ubuntu 8.10. On upgrading to Jaunty (9.04), sound stopped working through the docking station.

With or without speakers plugged into the docking-station headphone jack, sound now comes through the notebook built-in speakers. If I plug the speakers into the notebook headphone jack, the notebook built-in speakers are correctly disabled and sound comes through the external speakers (albeit with slightly poor quality).

I have also tried reinstalling Jaunty 9.04 from scratch (in case the problem was somehow due to the upgrade process), but the problem is unchanged.

I've read some posts about selecting the IEC958 switch in the volume control (through the Volume|Preferences button), but this option does not exist.

Output of "aplay -l":

**** List of PLAYBACK Hardware Devices ****
card 0: Intel [HDA Intel], device 0: STAC92xx Analog [STAC92xx Analog]
Subdevices: 1/1
Subdevice #0: subdevice #0

Output of "cat /proc/asound/card0/codec#* | grep Codec":

Codec: IDT 92HD71B7X
Codec: Conexant ID 2c06

I have also tried, without success, the following (using "model=dell-m4-1" and even variations m41, m4-2, ...) as suggested on the thread https://bugs.launchpad.net/ubuntu/+s...ux/+bug/258630

1. create/edit file "/etc/modprobe.d/sound" and change the content to:
options snd-hda-intel model=dell-m22 enable=1 index=0
alias snd-card-0 snd-hda-intel
alias sound-slot-0 snd-hda-intel

2. reboot

cat /proc/asound/modules:

 0 snd_hda_intel
 1 snd_usb_audio

cat /proc/asound/cards:

 0 [Intel ]: HDA-Intel - HDA Intel
                      HDA Intel at 0xf6fdc000 irq 21
 1 [Q9000 ]: USB-Audio - QuickCam Pro 9000
                      Logitech, Inc. QuickCam Pro 9000 at usb-0000:00:1a.7-4.1.2, high speed

lspci:

00:00.0 Host bridge: Intel Corporation Mobile 4 Series Chipset Memory Controller Hub (rev 07)
00:01.0 PCI bridge: Intel Corporation Mobile 4 Series Chipset PCI Express Graphics Port (rev 07)
00:19.0 Ethernet controller: Intel Corporation 82567LM Gigabit Network Connection (rev 03)
00:1a.0 USB Controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #4 (rev 03)
00:1a.1 USB Controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #5 (rev 03)
00:1a.2 USB Controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #6 (rev 03)
00:1a.7 USB Controller: Intel Corporation 82801I (ICH9 Family) USB2 EHCI Controller #2 (rev 03)
00:1b.0 Audio device: Intel Corporation 82801I (ICH9 Family) HD Audio Controller (rev 03)
00:1c.0 PCI bridge: Intel Corporation 82801I (ICH9 Family) PCI Express Port 1 (rev 03)
00:1c.1 PCI bridge: Intel Corporation 82801I (ICH9 Family) PCI Express Port 2 (rev 03)
00:1c.2 PCI bridge: Intel Corporation 82801I (ICH9 Family) PCI Express Port 3 (rev 03)
00:1d.0 USB Controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #1 (rev 03)
00:1d.1 USB Controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #2 (rev 03)
00:1d.2 USB Controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #3 (rev 03)
00:1d.7 USB Controller: Intel Corporation 82801I (ICH9 Family) USB2 EHCI Controller #1 (rev 03)
00:1e.0 PCI bridge: Intel Corporation 82801 Mobile PCI Bridge (rev 93)
00:1f.0 ISA bridge: Intel Corporation ICH9M-E LPC Interface Controller (rev 03)
00:1f.2 RAID bus controller: Intel Corporation Mobile 82801 SATA RAID Controller (rev 03)
00:1f.3 SMBus: Intel Corporation 82801I (ICH9 Family) SMBus Controller (rev 03)
01:00.0 VGA compatible controller: nVidia Corporation Quadro NVS 160M (rev a1)
03:01.0 CardBus bridge: Ricoh Co Ltd RL5c476 II (rev ba)
03:01.1 FireWire (IEEE 1394): Ricoh Co Ltd R5C832 IEEE 1394 Controller (rev 04)
03:01.2 SD Host controller: Ricoh Co Ltd R5C822 SD/SDIO/MMC/MS/MSPro Host Adapter (rev 21)
0c:00.0 Network controller: Intel Corporation Wireless WiFi Link 5100

lsmod | grep -i snd

snd_usb_audio 90400 1
snd_hda_intel 435636 3
snd_pcm_oss 46336 0
snd_mixer_oss 22656 1 snd_pcm_oss
snd_pcm 82948 3 snd_usb_audio,snd_hda_intel,snd_pcm_oss
snd_seq_dummy 10756 0
snd_usb_lib 24320 1 snd_usb_audio
snd_seq_oss 37760 0
snd_seq_midi 14336 0
snd_rawmidi 29696 2 snd_usb_lib,snd_seq_midi
snd_seq_midi_event 15104 2 snd_seq_oss,snd_seq_midi
snd_hwdep 15108 1 snd_usb_audio
snd_seq 56880 6 snd_seq_dummy,snd_seq_oss,snd_seq_midi,snd_seq_midi_event
snd_timer 29704 2 snd_pcm,snd_seq
snd_seq_device 14988 5 snd_seq_dummy,snd_seq_oss,snd_seq_midi,snd_rawmidi,snd_seq
snd 62628 19 snd_usb_audio,snd_hda_intel,snd_pcm_oss,snd_mixer_oss,snd_pcm,snd_seq_oss,snd_rawmidi,snd_hwdep,snd_seq,snd_timer,snd_seq_device
snd_page_alloc 16904 2 snd_hda_intel,snd_pcm
soundcore 15200 1 snd

cat /etc/modprobe.d/alsa-base.conf

# autoloader aliases
install sound-slot-0 /sbin/modprobe snd-card-0
install sound-slot-1 /sbin/modprobe snd-card-1
install sound-slot-2 /sbin/modprobe snd-card-2
install sound-slot-3 /sbin/modprobe snd-card-3
install sound-slot-4 /sbin/modprobe snd-card-4
install sound-slot-5 /sbin/modprobe snd-card-5
install sound-slot-6 /sbin/modprobe snd-card-6
install sound-slot-7 /sbin/modprobe snd-card-7

# Cause optional modules to be loaded above generic modules
install snd /sbin/modprobe --ignore-install snd $CMDLINE_OPTS && { /sbin/modprobe --quiet --use-blacklist snd-ioctl32 ; /sbin/modprobe --quiet --use-blacklist snd-seq ; }
#
# Workaround at bug #499695 (reverted in Ubuntu see LP #319505)
install snd-pcm /sbin/modprobe --ignore-install snd-pcm $CMDLINE_OPTS && { /sbin/modprobe --quiet --use-blacklist snd-pcm-oss ; : ; }
install snd-mixer /sbin/modprobe --ignore-install snd-mixer $CMDLINE_OPTS && { /sbin/modprobe --quiet --use-blacklist snd-mixer-oss ; : ; }
install snd-seq /sbin/modprobe --ignore-install snd-seq $CMDLINE_OPTS && { /sbin/modprobe --quiet --use-blacklist snd-seq-midi ; /sbin/modprobe --quiet --use-blacklist snd-seq-oss ; : ; }
#
install snd-rawmidi /sbin/modprobe --ignore-install snd-rawmidi $CMDLINE_OPTS && { /sbin/modprobe --quiet --use-blacklist snd-seq-midi ; : ; }
# Cause optional modules to be loaded above sound card driver modules
install snd-emu10k1 /sbin/modprobe --ignore-install snd-emu10k1 $CMDLINE_OPTS && { /sbin/modprobe --quiet --use-blacklist snd-emu10k1-synth ; }
install snd-via82xx /sbin/modprobe --ignore-install snd-via82xx $CMDLINE_OPTS && { /sbin/modprobe --quiet --use-blacklist snd-seq ; }

# Load saa7134-alsa instead of saa7134 (which gets dragged in by it anyway)
install saa7134 /sbin/modprobe --ignore-install saa7134 $CMDLINE_OPTS && { /sbin/modprobe --quiet --use-blacklist saa7134-alsa ; : ; }
# Prevent abnormal drivers from grabbing index 0
options bt87x index=-2
options cx88_alsa index=-2
options saa7134-alsa index=-2
options snd-atiixp-modem index=-2
options snd-intel8x0m index=-2
options snd-via82xx-modem index=-2
options snd-usb-audio index=-2
options snd-usb-us122l index=-2
options snd-usb-usx2y index=-2
options snd-usb-caiaq index=-2
# Ubuntu #62691, enable MPU for snd-cmipci
options snd-cmipci mpu_port=0x330 fm_port=0x388
# Keep snd-pcsp from beeing loaded as first soundcard
options snd-pcsp index=-2

uname -a :
Linux correa 2.6.28-11-generic #42-Ubuntu SMP Fri Apr 17 01:57:59 UTC 2009 i686 GNU/Linux

cat /proc/version_signature:
Ubuntu 2.6.28-11.42-generic