Losing KDE system notification sounds

From MEPIS Documentation Wiki

If you find that you no longer have the KDE start-up sound and that none of the notification sounds are working then you might have been hit with a known bug in KDE.

In your home folder is a file called:

~/.kde/share/config/knotifyrc

It should look like:

[StartProgress]
Arts Init=true
KNotify Init=true
Use Arts=true

But something in KDE's system can turn these to false and that's the end of the game. Set it back to the above and restart the session (via a logout, end session) and all is well.