It was set to fill flash. I might be that the ambient light was the reasons, I did take some pictures without the flash without any problems, just higher ISO.
Ah, that's it then. Fill flash "helps" the ambient light, it doesn't overpower it. If you want sharp pictures in dark(er) situations, you'd have to have the flash as the 'master' light, not the ambient.
I use fill flash for example for indoor parties, where i use a higher ISO and a little pop of flash to bring more life to the picture, but the heavy lifting is then done by the ambient light.
Of course, YMMV
