advanced poll 2.0 fatal error

i am getting the following:

Fatal error: Failed opening required '//include/config.inc.php' (include_path='') in /booth.php on line 24

is there something i need to change within booth.php or the common.inc.php? everything else seems to work.

i am using textfile instead of db.

the booth.php follows:

<?php

$include_path = dirname(__FILE__);

if (!isset($PHP_SELF)) {
$PHP_SELF = $HTTP_SERVER_VARS["PHP_SELF"];
if (isset($HTTP_GET_VARS)) {
while (list($name, $value)=each($HTTP_GET_VARS)) {
$$name=$value;
}
}
if (isset($HTTP_POST_VARS)) {
while (list($name, $value)=each($HTTP_POST_VARS)) {
$$name=$value;
}
}
if(isset($HTTP_COOKIE_VARS)){
while (list($name, $value)=each($HTTP_COOKIE_VARS)){
$$name=$value;
}
}
}

require $include_path."/include/config.inc.php";
require $include_path."/include/class_poll.php";

$php_poll = new poll();
$php_poll->set_include_path($include_path);

?>