WordPress 404 error when running this page

I am trying to do a post from the frontend of WordPress. I have the following code in a page called page-submit.php and while it has worked, I get 404 errors when the page is submitted but I don’t know why or how to trace the issue.

This page page_submit.php shows up fine and is located in my theme folder.

Any suggestions?

<?php get_header(); ?>

<?php

// Check if the form was submitted
if( 'POST' == $_SERVER['REQUEST_METHOD'] && !empty( $_POST['action'] )) {

// Do some minor form validation to make sure there is content
if (isset ($_POST['title'])) { 
    $title =  $_POST['title']; 
} else { 
    echo 'Please enter a title';
}
if (isset ($_POST['description'])) { 
    $description = $_POST['description']; 
} else { 
    echo 'Please enter the content'; 
}
$tags = $_POST['post_tags'];

// Add the content of the form to $post as an array
$post = array(
    'post_title'    => $title,
    'post_content'  => $description,
    'post_category' => $_POST['cat'],  // Usable for custom taxonomies too
    'tags_input'    => $tags, 
    'post_status'   => 'publish',           // Choose: publish, preview, future, etc.
    'post_type'     => $_POST['post_type']  // Use a custom post type     if you want to
);
wp_insert_post($post);  // Pass  the value of $post to WordPress the insert function
                        // http://codex.wordpress.org/Function_Reference/wp_insert_post

wp_redirect( home_url() ); // redirect to home page after submit

} // end IF
// Do the wp_insert_post action to insert it
do_action('wp_insert_post', 'wp_insert_post'); 
?>



<!-- New Post Form -->
<div id="postbox">
<form id="new_post" name="new_post" method="post" action="">

    <p><label for="title">Title</label><br />
    <input type="text" id="title" value="" tabindex="1" size="20" name="title"     />
    </p>
    <p><label for="description">Description</label><br />
    <textarea id="description" tabindex="3" name="description" cols="50" rows="6"></textarea>
    </p>
    <p><?php wp_dropdown_categories( 'show_option_none=Category&tab_index=4&taxonomy=category' ); ?></p>
    <p><label for="post_tags">Tags</label>
        <input type="text" value="" tabindex="5" size="16" name="post_tags" id="post_tags" /></p>
    <p align="right"><input type="submit" value="Publish" tabindex="6" id="submit" name="submit" /></p>

    <input type="hidden" name="post_type" id="post_type" value="post" />
    <input type="hidden" name="action" value="post" />
    <?php wp_nonce_field( 'new-post' ); ?>
</form>
</div>
<!--// New Post Form -->


<?php get_sidebar(); ?>

<?php get_footer(); ?>