In app/design/frontend/default/default/template/page/html/header.phtml add the following code:
<?php echo $this->getChildHtml('cart_link_container') ?>
in the page.xml add the following code:
<block type="page/html_header" name="header" as="header">
.
.
.
<block type="page/template_links" name="cart_link_container" as="cart_link_container">
<block type="checkout/links" name="cart_link">
<action method="addCartLink"></action>
</block>
</block>
.
.
.
</block>