After upgrading to Intrepid Ibex I found a little problem, the flash videos that you play in youtube.com didn't have any sound and basically any flash sound was gone. After a little research I found this post that offers a very good solution, sadly is only a temporary solution. Every time you start Ubuntu you will need to do this. Basically what it tells you to do is to kill the process pulseaudio and then to re load the alsa process. To do this you need to type the following instructions:

sudo killall pulseaudio

sudo alsa force-reload

You can find the original post in this web site:http://bryandunn.com/uncategorized/fixing-flash-sound-in-ubuntu-intrepid...

After trying a little bit more I found that the main problem comes form the flash version, somehow after the Ubuntu upgrade the flash player is still the previous one, so what you need to do is to force the upgrade, just type:

sudo apt-get install flashplugin-nonfree

Hope this will work for you as it worked for me =)