As for the email responses, if you click the subscribe link at the bottom you will be emailed on the repsonses.
I was hoping thta somone else that uses Kubuntu could help you, but it is time for me to chime in.
I am having a simiilar issue when running KDE4 on another distro, my issue is caused when I have any media player running in the background, even when it is stopped I will not get broweser audio. This issue is caused because a specific application is tying up the audio device file.
Please check to make sure that you don't have xmms, audacous or amarok running when you try to get browser audio to try to single out the cause of the issue.
Please report your findings, I suspect that if that is not the case then we will need to see a lsof output to see what is locking the audio device file.