I answer to myself just in case somebody else is also having the problem: instead of restarting the session (or rebooting), it's much more convenient just to kill kded4 and re-execute it again from krunner.
I answer to myself just in case somebody else is also having the problem: instead of restarting the session (or rebooting), it's much more convenient just to kill kded4 and re-execute it again from krunner.