- No instances of Dolphin would start
- The kickoff launcher would not work
- The KDE activity manager was crashing.
I suspected the Nepomuk might be the culprit and I was right. I stopped it by running
qdbus org.kde.NepomukServer /nepomukserver quit
I then wiped out its data by running
rm -r .kde/share/apps/nepomuk/
Finally I got it started again by runing
…and my problems were solved.
Trying to search for a solution to this problem, I found people suggesting that one would wipe the ~/.kde folder and start afresh. That sounded too drastic and a great deal of my customizations would have been lost in the process.