header already sent error

I am having a little trouble with the settings page in the template I am working on.

In the function.php file I have a hook that creates an “Theme Options” page that allows admin to upload a new header image for the theme.

The problem is that the functions page is causing problems with the rest of the admin site.

Whenever I try and create a new page I get a header already sent error.

Warning: Cannot modify header information - headers already sent by (output started at /home/clubsdot/public_html/wp-content/themes/subway/functions.php:59)

Below is a copy of my functions file, this has me stumped, anyone knows what is causing the problem?

Thanks,
Levi Putna

<?php
// Hook for adding admin menus
add_action('admin_menu', 'add_menu');

function add_menu() {
   add_theme_page(__('Theme Options'), __('Theme Options'), 8, basename(__FILE__), theme_options);
}

function theme_options(){
?>
<div class="wrap">
<h>
	<h2>Current Theme Options</h2>

	<form id="post" method="POST" enctype="multipart/form-data" action="" name="post">
		<div class="wrap">
			<div id="poststuff">
            <br />
				<div id="submitpost" class="submitbox">
                	<div class="inside">
                    <h4>Header image</h4>
                    <p>Header images must be in jpg format with a minimum width of 800px and a height of 200px.</p>
                	</div>
                    <p class="submit">
                    	<input id="save-post" class="button button-highlighted" type="submit" tabindex="4" value="Save" name="save"/>
						<br class="clear"/>
                    </p>
                </div>
                <div id="post-body">
                    <div id="titlediv">
                    	<h3>Header Image</h3>
                        <div id="titlewrap">
                          <input id="header_image" type="file" c name="header_image" tabindex="1" size="96" />
                        </div>
                        <?php
                       if($_POST){
                            if (is_uploaded_file($_FILES['header_image']['tmp_name'])){
    include_once($sStyleFolder . 'images/header/generator.php');
    $header =  generateHeader($sStyleFolder, $_FILES['header_image']);
}
                        }

			?>
                    </div>
                </div>
			</div>
		</div>
	</form>

</div>

<?php
}

?>

<?php
if ( function_exists('register_sidebar') )
register_sidebar(array('name'=>'Page_Sidebar',
'before_widget' => '',
'after_widget' => '',
'before_title' => '<h3>',
'after_title' => '</h3>',
));

register_sidebar(array('name'=>'Post_Sidebar',
'before_widget' => '',
'after_widget' => '',
'before_title' => '<h3>',
'after_title' => '</h3>',
));

register_sidebar(array('name'=>'Search_Sidebar',
'before_widget' => '',
'after_widget' => '',
'before_title' => '<h3>',
'after_title' => '</h3>',
));

register_sidebar(array('name'=>'Single_Sidebar',
'before_widget' => '',
'after_widget' => '',
'before_title' => '<h3>',
'after_title' => '</h3>',
));

register_sidebar(array('name'=>'Header',
'before_widget' => '',
'after_widget' => '',
'before_title' => '<h3>',
'after_title' => '</h3>',
));

?>