I've uploaded the image files again, but it didn't solve it. However I think the problem might be because my upload folder by default is in the root of my domain above the forum folder. In the admin section I therefore had to give the path to the upload folder as ../upload
Could that cause a problem when the application calls for images in the posts. If I should correct an image path location, in which file(s) should I look then?
I should mention that the application correctly creates a temp folder in my upload folder (above the forum folder).