Sorry Barry , but I do not use the "photobucket" so I can't answer for sure....
I do know I had the same thing happen when I put my link in the "2nd box" when you post titled "optional Image URL" and had to stick with the first "optional link URL" and gave it a link title.
OR
usiung "imageshack" its gives you several options .. if I picked the wrong one or as Mark or someone said did not first clear off the existing "http: wording on the line before pasting my link I had the same resulst you are getting.
BUT , I am waiting on the pic you are trying to post with anticipation so I hope someone can help