It may be exactly what it says here - no default folder assigned. The other person doing the import probably has a folder listed under volume (on the second screenshot, you can see it says "<use parent folder's default volume>"

If you only have one volume, I'd go into the root of your repository, go to folder properties, then the folder tab, then select your voilume (by default this is named default).

If you do use multiple volumes, go to the highest level you want all the documents in and set it there. It should inherit down into any folders under it. (i believe - I know it will for new folders). If it doesn't do it for existing folders you'll have to go into all of them and fix it. 

You could do a search for all folders on your system and then display the default volumne column to spot ones that don't have one set.