You may be able to resolve this with a simple hack to your tpl_header.php file.

(The original of this resides in templates/template_default/common/tpl_header.php , so you'll need to make a copy of it, then save it to: templates/YOUR-CUSTOM-TEPLATE/common/tpl_header.php).

Find the following...

PHP Code:
<?php } // no HEADER_SALES_TEXT or SHOW_BANNERS_GROUP_SET2 ?>
</div>
<br class="clearBoth" />
<!--eof-branding display-->
... and try COMMENTING OUT the <br class...> bit...

PHP Code:
<?php } // no HEADER_SALES_TEXT or SHOW_BANNERS_GROUP_SET2 ?>
</div>
<!-- <br class="clearBoth" /> -->
<!--eof-branding display-->
If you use categories-tabs (categories in the header) or banners under the header, this may cause problems. Try it and see if it suits your needs.