KDE Plasma desktop crash on start (faulty widget)

I have placed a rather nice looking world clock widget on my screen the second I found it, unfortunately after some time it broke down, and no cache clearing helped.

What did help me was:

1. in console, move the offending widget to temporary location:
   mv /usr/share/kde4/services/plasma-applet-worldclock.desktop /tmp/
2. CTRL+ALT+DELETE -> Log out
3. Select KDE session (Failsafe)
4. Log back in
5. I could see an empty "widget window", which now could be removed from the screen.
6. again log out, 
7. Chose normal KDE session
8. log back in
9. mv /tmp/plasma-applet-worldclock.desktop /usr/share/kde4/services/
10. chose the widget from the widget list and place it back on the screen

Note, that your widget might be in different location, but this should help with most of them.