When I put the image field in a field group that node suddenly showed the newly added images. But old nodes still don't show any of the images.

What do you mean with "broken my site"? Is there nothing I can do except add all the images again?

I installed the pathauto module on your advice. It can't be that module that messes up the paths?

Now the images for each node in view mode seems to be rebuilt. But still don't show in node edit mode. If I open a node, and re-submit it, the node all of a sudden shows 2 identical images. One of them now shows in node edit mode, the other one is untouchable. Where can such doubled information be stored in the database?

I'll send you a PM with some info.
Thanks for the help.