It *could* be that it's running into an error and php is configured to not display errors to the browser. If you have access to the php.ini file you can check this, I believe it's display_errors or something like that.
As for dumping the contents of the database and starting fresh. Basically all you need to do is drop all of the tables or the entire database if UBB.threads is the only thing inside and then rerun the install/createtable.php script.
