Please post a screen shot of what you are seeing.
There is an option in the import dialog to include Subfolder. Maybe you should uncheck that option and test.
What exact folder have you selected when this happens?
Don't know how to do do that screen shot. The non-pictures are appearing rapidly in the grid and files are being listed/added in the navigator. After I see whats happening - done that several times - I just cancel and don't back-up that mess.
All the folders have sub-folders which have sub-sub-folders --- There are probably a 1000 or more folders in the primary 11 main sub-folders.
If you right click on the folder you can select, actually deselect Include subfolders. Have you tried that.
What kind of computer are you using, Mac or Windows? On Mac the Shift+Command+4 keys allows you to draw a window around what you want to capture in a screen shot and saves it to your desktop. On windows use the Snipping Tool (Start button, Type Snipping Tool, hit the enter key or click the Snipping tool shortcut).