Hi,
When you set up the forum, alot of background coding is changed in the many different files which points to the original directory. Changing files after the creation of such a forum leads to huge big headaches.
I suggest the following:
I) Delete the entire forum and start a fresh, making sure all directorys are named correctley before you start
II) Start a help desk ticket and ask for the backup to installed. This should restore your forums, but anything you changed anywhere on your site since the backup will be lost
Jim