no WYSIWYG editor when get-a-post plugin is enabled

Hello, i’m running wordpress 2.2.1 and several plugins, in which GET-A-POST R1.3.

I’ve noticed that the WYSIWYG (rich text) editor is broken when GET-A-POST is enabled.
Firefox tells me

Erreur : realTinyMCE is not defined
Fichier source : http://***/wordpress/wp-includes/js/tinymce/tiny_mce_gzip.php?ver=20070326
Ligne : 43

It’s really strange becauses the plugins seems very simple; no javascript, one single file, etc.

Here’s the code. I can’t find what is the matter…

function get_a_post($id='GETPOST') {
    global $post, $tableposts, $wp_version, $wpdb;

    if($wp_version < 1.5)
        $table = $tableposts;
    else
        $table = $wpdb->posts;

    $now = current_time('mysql');
    $name_or_id = '';

    if(!$id || 'GETPOST' == $id) {
        if($wp_version < 2.1)
            $query_suffix = "post_status = 'publish'";
        else
            $query_suffix = "post_type = 'post' AND post_status = 'publish'";
    } elseif ('GETPAGE' == $id) {
        if($wp_version < 2.1)
            $query_suffix = "post_status = 'static'";
        else
            $query_suffix = "post_type = 'page' AND post_status = 'publish'";
    } elseif ('GETSTICKY' == $id) {
        if($wp_version < 1.5)
            $table .= ', ' . $tablepostmeta;
        else
            $table .= ', ' . $wpdb->postmeta;
        $query_suffix = "ID = post_id AND meta_key = 'sticky' AND meta_value = 1";
    } else {
        $query_suffix = "(post_status = 'publish' OR post_status = 'static')";

        if(is_numeric($id)) {
            $name_or_id = "ID = '$id' AND";
        } else {
            $name_or_id = "post_name = '$id' AND";
        }
    }

    $post = $wpdb->get_row("SELECT * FROM $table WHERE $name_or_id post_date <= '$now' AND $query_suffix ORDER BY post_date DESC LIMIT 1");

    get_post_custom($post->ID);

    if($wp_version < 1.5)
        start_wp();
    else
        setup_postdata($post);
}