Have you been able to you sort it out? If not, check if you have added the following code to the end of your application_top.php (the one in your shop root directory):
/* Add to /catalog/includes/application_top.php at the end of the file right before the last question mark*/
require(DIR_WS_FUNCTIONS . 'clean_html_comments.php');
require(DIR_WS_FUNCTIONS . 'header_tags.php');
I forgot this and thus received exactly the same error.
Hth,
10 little orcs