includes/modules/ezpages_bar_header.php

I believe the error maybe in the above file

Line #51 : zen_href_link(FILENAME_EZPAGES, 'id=' . $page_query->fields['pages_id'] . '&chapter=' . $page_query->fields['toc_chapter'], ($page_query->fields['page_is_ssl']=='0' ? 'NONSSL' : 'SSL')) :

This is the line where the header is written. It seems when you try to link to an existing file it won't work. Like a Contact Us link pointing to a Contact Us file. But if it's something you wrote using EZ pages links then it's ok. Hope someone knows the coding better than me