Sometimes the KDE notifier shows up an error that freeze up plasma creating a bucle for infinite notices saying the same thing: “Unable to create io-slave: klauncher said: unknown protocoll <<amarok-sqltrackuid>>”.
Seems that the amarok config files for plasma that I removed wasn’t the solution (#2). Some hours later the plasma notifier began again with the amarok i/o error. Don’t know where would be the reason for Amarok to get that confused.
All my music collection is in the user (/home/user) folder.
I have unchecked the two options you suggest so I’ll wait now if the notification shows up again.