Attachment thumbnails dont show on post, but show in quick editor

[KaitenV]

I am trying to attach an image to my post and it shows up in the editor, but it's a broken image when you view the thread.

http://otakuhelpers.com:8080/forums/...d-cars?p=71289

edit: I edited "View Attached Images Inline" to "yes, full size" and it does work. However, why does "Yes, display thumbnails" only show a link with no image?