Magento 1.7.0.2 Catalog Google Sitemap 404 Error – Fix Guide

Try this.

Edit the app/design/frontend/your_package/your_theme/template/catalog/seo/tree.phtml file in your theme. Add an if condition just after the foreach loop which checks for activeness of the $_item.

<?php $_items = $this->getCollection(); ?>
<?php if($_items->getSize()): ?>
    <ul class="sitemap">
        <?php foreach ($_items as $_item): ?>
          <?php if( $_item->is_active ) : ?> 
            <li class="level-<?php echo $this->getLevel($_item) ?>" <?php echo $this->getLevel($_item)?'style="padding-left:' . $this->getLevel($_item, 2) . '0px;"':'' ?>><a href="<?php echo $this->getItemUrl($_item) ?>"><?php echo $_item->name ?></a></li>
        <?php endif; ?> 
        <?php endforeach; ?>
    </ul>
<?php else: ?>
    <p class="note-msg">
        <?php echo $this->__('There are no %s available.', $this->getItemsTitle()); ?>
    </p>
<?php endif ?>

The Magento Connect Manager is an independent web app placed in downloader inside magento root, depending on your webserver configuration you have to create rewrites there, it only gets login state and some configs from magento, its not build on top of magento.