As right now, as I cannot figure out what goes wrong AND if you are still determined to find out what goes on, you can do the following trick I did when creating the application.
This guarantees you gonna see results
Please use Charles:
http://www.xk72.com/charles/ (free to try, http proxy).
You have to set up Charles, start it, configure it to run a proxy on some port, let's say 8000, and then use Java SMF Backup to actually do backups using the proxy localhost on port 8000.
Charles will meticulously show you what JSB will send to the forum and what pages the server will answer.
If you don't mind a debug session and watch a lot of data going on, it can help you.
At this moment I cannot do anything, because from the IP I try to connect to you I still get authorization failed (403) which I shown you in my posts above [for the new forum too]
Please keep me posted
I'd like to hear what went wrong and post it here on the site.