Be sure you updated all PATHS in the file to be your document root (vs /forums)

Your paths area should look something like:
'FULL_URL' => 'http://yoursite.tld',
'BASE_URL' => '',
'FULL_PATH' => '/home/youruseraccount/public_html',
'SESSION_PATH' => '/home/youruseraccount/public_html/sessions',

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