Yeah, the attachment directory on the forums is messed up again..Its the same cause of the avatars not working. I've been avoiding doing too much to try and correct the issue, out of fear of breaking the forums worse!
As Last Rites mentioned, you would be better off using an external photo hosting service rather than attaching then to your posts. I'm sorry for the inconvenience! For some reason, the attachment hosting features of the forum software have been very unstable.