This used to work in karmic and recently it stopped working.

In system settings -> Desktop Search. Under strigi desktop file indexer it says.

"The name org.kde.nepomuk.services.nepomukstrigiservice was not provided by any .services file".

Your system configuration is inconsistent. If you are using official packages, then please report this at Launchpad after ensuring that all packages have been fully updated.

You may wish to restart or log out of your system to ensure that any upgraded files are correctly detected by system-wide services such as D-Bus.

Something strange happened. My plasma froze completely( was using firefox) . Nothing was responding.
I did a VT switch and restarted kdm. Alas strigi started working again.

No restarts or shut down helped, but a simple kdm restart.