I have been trying to contact you, maybe I finally found the right place. It's confusing.
I have been using ImageProxy for 8 months and recently, like in the last few days, Photobucket images have started to appear as "broken image" icons instead of the image itself, in posts.
In the editor, the images appear perfect.
But once you save the post, they are broken.
So, the cache is not working, for Photobucket images.
The Photobucket URLs have always been strange -- ending in HTML not JPG for example -- but it has always worked before now.
Example post: http://edgematters.uk/thread/2725-ivory-micarta-trapper/?postID=27792#post27792