The issue is that I'm using the little 'Insert Image' formatting tool when creating a post. The Dropbox share picture code is inserted into the post, which should result in a picture showing up in the post.
I put the link URL, using the 'Insert Link' formatting tool in this post (other than my typo from working too late) so that it could be validated that the URL is good, ie not restricted by permissions.
The failure is:
when I use the 'Insert Image' http ://my picture link from dropbox it does not insert a picture in the post.
when I use the 'Insert Image' http ://my picture link from forums album it does insert a picture in the post.
(It's hard to describe all this, if I actually use the CODE as an example, nothing happens. Hence the above screen shot)