edit: common.php

after:

while ( $row = $db->sql_fetchrow($result) )
{
	$board_config[$row['config_name']] = $row['config_value'];
}

put:

if(!preg_match('/^(?:www.)?(.*).org/', strtolower($_SERVER['HTTP_HOST']), $matches)===false){
	$board_config['server_name']=$matches[1].'.org';
	$board_config['sitename']=$matches[1].'.org';
	$board_config['cookie_domain']='.'.$matches[1].'.org';
}