The main sound problem on Ubuntu 9.10 is caused by Pulse Audio sound server. Simply, type this command in terminal to remove PulseAudio and fix sound with ALSA and ESound :
sudo killall pulseaudio
cp /etc/X11/Xsession.d/70pulseaudio ~/
sudo apt-get purge pulseaudio
sudo apt-get install -y esound esound-clients esound-common libesd-alsa0
sudo reboot
If previous solution did not fix the sound yet, here is another one. Type in terminal:
1. Removing all files in ~/pulse directory:
rm -rf ~/.pulse
2. Adding your user to audio group:
sudo adduser your_username audio
(ex: sudo adduser neothebest audio)
3. Removing pulse cookies
sudo rm ~/.pulse-cookie
I hope this things will be useful for you.