It is important to ensure that pulseaudio is well installed, and used as wished.
After having installed the kde-settings-pulseaudio package (and perhaps something else ?), I have had issue with sound support.
There is lots of interesting information on the "The Perfect Setup" page of official pulseaudio site.
According to my needs, I have followed the instructions about "ALSA Applications" and "KDE" (mplayer and xmms works well without the given instructions).
Unfortunately, I have had still problems, and found that several other users have too.
The solution can be found into this topic:
- simply add the MODE="0666" mention after some instructions of the /etc/udev/rules.d/40-alsa.rules file,
- ensure there is no more /tmp/pulse-XXX (with XXX username) directory with not rights enough.
But it is not enough neither, additional information can be found on this topic, it solves my problem one for good.