Yikes! The picture above was taken just after the only change you did was try to add an image to the forum title? My guess is that the only way to fix that is going to be to go into the database to fix it.
I saw you posted this over on vb.com also. If you aren't comfortable accessing your database, it may be the best thing to do is to put in a support ticket. If you are comfortable accessing the database, it is in the forum table and the column name is title.
I don't know how bad your problem is. Can you get to the Forum Manager page that lists the forums? If so, then you may select Delete Forum from the dropdown menu.