Actually it was a Popular Posts section. I have no idea what happened.
It looked good in the widget area, then I had a look at the complete front page.
All the categories had been duplicated in the header section.
I couldn't get rid of them and asked for help from the My Theme Shop team.
It took a day but they got it done.
Probably I would still be scratching my head if not for them.
So a big thank you to them.