I've been pulling my hair out over this problem.

I'm running Ubuntu 10.04 on a second drive as a separate partition on my PC. The
primary OS is Windows XP Professional.

When I first installed Ubuntu, the version was 9.xx. After upgrading I was able
to get Flash to work, but I did not have audio.

I started playing with alsa when I was researching the problem, and then I lost
alsamixer.

So, I followed the instructions provided by another Ubuntu user, and completely
uninstalled/reinstalled alsa.

After reinstalling it, the alsamixer was back, and I had audio.

Then, I shutdown my system for the night. When I brought the system back up,
there wasn't any audio AND there hasn't been any audio since.

Here are some details about the audio portion of my Ubuntu configuration.

Sound card info:

!!Soundcards recognised by ALSA
!!-----------------------------

0 [ICE1724 ]: ICE1724 - ICEnsemble ICE1724
ICEnsemble ICE1724 at 0xbc00, irq 18
1 [U0x93a0x2620 ]: USB-Audio - USB Device 0x93a:0x2620
USB Device 0x93a:0x2620 at usb-0000:00:10.2-1, full speed

root@mike-desktop:~# modprobe snd-hda-intel && speaker-test

speaker-test 1.0.24.2

Playback device is default
Stream parameters are 48000Hz, S16_LE, 1 channels
Using 16 octaves of pink noise
ALSA lib pcm_direct.c:980:(snd1_pcm_direct_initialize_slave) unable to install
hw params
ALSA lib pcm_dmix.c:1030:(snd_pcm_dmix_open) unable to initialize slave
Playback open error: -16,Device or resource busy