I had a problem with pulseaudio one time when I changed soundcards. What I did was to delete the files that are located in the ~/.pulse folder, then the sound worked like a charm.
the ~/.pulse folder contains the settings for each user. (it's the folder in each user's home folder.. for example.. For the user "Me" it would be located at /home/Me/.pulse)
You can try deleting the items in that folder, and if it still doesn't work, then it's probably a system global default problem you are having. (the global system files are located in /etc/pulse but don't go deleting those. )