How Do I Fix The Sort Order Of My Posts?

… I found this Plugin which fixed the problem on my blog:

<?php
/*
Plugin Name: 123 No Group By ID
Plugin URI:
Description: Changes the GROUP BY id in GROUP BY post_date (Problem from MySQL 5.0.51).
Author: Ingo Henze
Version: 0.10
Author URI: http://putzlowitsch.de/
*/ 

    // GROUP BY auswerten
    function plw123ngb_posts_groupby( $groupby ) {
        if( preg_match( "/(|[ ,.])id(|[ ,])/i", $groupby ) )
            $groupby = 'post_date';
        return $groupby;
    }

    add_filter( 'posts_groupby', 'plw123ngb_posts_groupby' );

?>