I think there is a problem with the authentication on the forum (it redirects to some other page when something goes wrong and then the application won't find the sesc (or sc) parameter in the page).
I cannot ask to see the log files as they do contain your sensitive information..
What you should do is install an HTTP proxy (such as Charles
http://www.xk72.com/charles/ - it's shareware, but you can use it for 30 days).
After you set it up, please set the proxy parameters in Java SMF Backup to point to localhost and the port you have started Charles on.
Then watch the dialog between the application and your forum, and then click on the last page that is sent back from the forum to the application.
You should be able to see (if you save the text from Charles to an .html page) what was the error message.
I guess it's something related to the session authentication - but can't actually say what goes wrong..
(i mean it's a trade off - no matter how much logging I can put in the application, only the user is able to investigate what goes on - as there are privacy issues to take into account).
I guess Charles is an easy solution.. You should see what is the page returned by the forum when you try to connect via the application (it will contain an error message sent by the forum instead of the admin page which has the sc or sesc parameter).
Hope this helps
please keep me posted.