try reinstallin phpbb (delete all the files remove db entries etc etc)
if that deosent work im not sure

btw i have large amounts of problems with my board on lycos i hope your hair grows quick cos youll probaly tear it out

this doesnt look right

(include_path='.:/data/apache/php/mmp_lib')

I think it should probably be

(include_path='.. /data/apache/php/mmp_lib')

This I have got in the file: common.php

<?php
if ( !defined('IN_PHPBB') )
{
	die("Hacking attempt");
}

error_reporting  (E_ERROR | E_WARNING | E_PARSE); // This will NOT report uninitialized variables
set_magic_quotes_runtime(0); // Disable magic_quotes_runtime

//
// addslashes to vars if magic_quotes_gpc is off
// this is a security precaution to prevent someone
// trying to break out of a SQL statement.
//
if( !get_magic_quotes_gpc() )
{
	if( is_array($HTTP_GET_VARS) )
	{
		while( list($k, $v) = each($HTTP_GET_VARS) )
		{
			if( is_array($HTTP_GET_VARS[$k]) )
			{
				while( list($k2, $v2) = each($HTTP_GET_VARS[$k]) )
				{
					$HTTP_GET_VARS[$k][$k2] = addslashes($v2);
				}
				@reset($HTTP_GET_VARS[$k]);
			}
			else
			{
				$HTTP_GET_VARS[$k] = addslashes($v);
			}
		}
		@reset($HTTP_GET_VARS);
	}

if( is_array($HTTP_POST_VARS) )
{
	while( list($k, $v) = each($HTTP_POST_VARS) )
	{
		if( is_array($HTTP_POST_VARS[$k]) )
		{
			while( list($k2, $v2) = each($HTTP_POST_VARS[$k]) )
			{
				$HTTP_POST_VARS[$k][$k2] = addslashes($v2);
			}
			@reset($HTTP_POST_VARS[$k]);
		}
		else
		{
			$HTTP_POST_VARS[$k] = addslashes($v);
		}
	}
	@reset($HTTP_POST_VARS);
}

if( is_array($HTTP_COOKIE_VARS) )
{
	while( list($k, $v) = each($HTTP_COOKIE_VARS) )
	{
		if( is_array($HTTP_COOKIE_VARS[$k]) )
		{
			while( list($k2, $v2) = each($HTTP_COOKIE_VARS[$k]) )
			{
				$HTTP_COOKIE_VARS[$k][$k2] = addslashes($v2);
			}
			@reset($HTTP_COOKIE_VARS[$k]);
		}
		else
		{
			$HTTP_COOKIE_VARS[$k] = addslashes($v);
		}
	}
	@reset($HTTP_COOKIE_VARS);
}
}

//
// Define some basic configuration arrays this also prevents
// malicious rewriting of language and otherarray values via
// URI params
//
$board_config = array();
$userdata = array();
$theme = array();
$images = array();
$lang = array();
$gen_simple_header = FALSE;

include('config.'.$phpEx);
include_path='../data/apache/php/mmp_lib'
if( !defined("PHPBB_INSTALLED") )
{
	header("Location: install.$phpEx");
	exit;
}

include('includes/constants.'.$phpEx);
include('includes/template.'.$phpEx);
include('includes/sessions.'.$phpEx);
include('includes/auth.'.$phpEx);
include('includes/functions.'.$phpEx);
include('includes/db.'.$phpEx);

//
// Mozilla navigation bar
// Default items that should be valid on all pages.
// Defined here and not in page_header.php so they can be redefined in the code
//
$nav_links['top'] = array ( 
	'url' => append_sid("index.".$phpEx),
	'title' => sprintf($lang['Forum_Index'], $board_config['sitename'])
);
$nav_links['search'] = array ( 
	'url' => append_sid("search.".$phpEx),
	'title' => $lang['Search']
);
$nav_links['help'] = array ( 
	'url' => append_sid("faq.".$phpEx),
	'title' => $lang['FAQ']
);
$nav_links['author'] = array ( 
	'url' => append_sid("memberlist.".$phpEx),
	'title' => $lang['Memberlist']
);

//
// Obtain and encode users IP
//
if( getenv('HTTP_X_FORWARDED_FOR') != '' )
{
	$client_ip = ( !empty($HTTP_SERVER_VARS['REMOTE_ADDR']) ) ? $HTTP_SERVER_VARS['REMOTE_ADDR'] : ( ( !empty($HTTP_ENV_VARS['REMOTE_ADDR']) ) ? $HTTP_ENV_VARS['REMOTE_ADDR'] : $REMOTE_ADDR );

if ( preg_match("/^([0-9]+\.[0-9]+\.[0-9]+\.[0-9]+)/", getenv('HTTP_X_FORWARDED_FOR'), $ip_list) )
{
	$private_ip = array('/^0\./', '/^127\.0\.0\.1/', '/^192\.168\..*/', '/^172\.16\..*/', '/^10..*/', '/^224..*/', '/^240..*/');
	$client_ip = preg_replace($private_ip, $client_ip, $ip_list[1]);
}
}
else
{
	$client_ip = ( !empty($HTTP_SERVER_VARS['REMOTE_ADDR']) ) ? $HTTP_SERVER_VARS['REMOTE_ADDR'] : ( ( !empty($HTTP_ENV_VARS['REMOTE_ADDR']) ) ? $HTTP_ENV_VARS['REMOTE_ADDR'] : $REMOTE_ADDR );
}
$user_ip = encode_ip($client_ip);

//
// Setup forum wide options, if this fails
// then we output a CRITICAL_ERROR since
// basic forum information is not available
//
$sql = "SELECT *
	FROM " . CONFIG_TABLE;
if( !($result = $db->sql_query($sql)) )
{
	message_die(CRITICAL_ERROR, "Could not query config information", "", __LINE__, __FILE__, $sql);
}

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

//
// Show 'Board is disabled' message if needed.
//
if( $board_config['board_disable'] && !defined("IN_ADMIN") && !defined("IN_LOGIN") )
{
	message_die(GENERAL_MESSAGE, 'Board_disable', 'Information');
}

?>

Can you find the missing link?

edit your index.php @ line 31

change
(include_path='.:/data/apache/php/mmp_lib')

to

(include_path='.. /data/apache/php/mmp_lib')

(courtesy of the big cheese)