the_content() doesn’t work…why?

Hi everyone,
i made the following template in order to create a private page and leave visible the link to all users, logged and not logged:

<?php
/*
Template Name: Pagina Privata
*/
?>
<?php get_header(); ?>
<?php get_sidebar();
$page_id = $_REQUEST['page_id'];
?>
<div class="content">

		<?php if(is_user_logged_in()): ?>

		<?php if (have_posts()) : while (have_posts()) : the_post(); ?>
		<div class="post" id="post-<?php echo $page_id ?>">
			<h4><?php the_title(); ?></h4>
			<?php the_content('<p class="serif">Read the rest of this page &raquo;</p>'); ?>
			<?php wp_link_pages(array('before' => '<p><strong>Pages:</strong> ', 'after' => '</p>', 'next_or_number' => 'number')); ?>
		</div>
		<?php endwhile; endif; ?>
	<?php edit_post_link('Edit this entry.', '<p>', '</p>'); ?>

		<?php else:?>
			<h4>Pagina protetta da password.</h4>
				<form name="loginform" id="loginform" action="http://localhost/area/wp-login.php" method="post">
				<p>
				<label>Nome utente<br />
				<input type="text" name="log" id="user_login" class="input" value="" size="20" tabindex="10" /></label>
				</p>
				<p>
				<label>Password<br />
				<input type="password" name="pwd" id="user_pass" class="input" value="" size="20" tabindex="20" /></label>
				</p>
				<p class="forgetmenot"><label><input name="rememberme" type="checkbox" id="rememberme" value="forever" tabindex="90" /> Ricordami</label></p>
				<p class="submit">
				<input type="submit" name="wp-submit" id="wp-submit" class="button-primary" value="Collegati" tabindex="100" />
				<input type="hidden" name="redirect_to" value="<?php bloginfo('url');?>/?page_id=<?php echo $page_id;?>" />
				<input type="hidden" name="testcookie" value="1" />
	</p>
</form>

		<?php endif; ?>

</div>
<div class="clear"></div>
<?php get_footer(); ?>

why i can’t see the page content?