Yes, I was wondering if there was a little misunderstanding, or that I may have confused the issue. Here's the current situation:
Header Tags is installed and the default tags (from the Text Control page) work well.
When the Fill Tags page is used to fill tag entries for Products, all my product pages come up blank. (Selecting "Fill All Tags" for Categories or Manufacturers does not product blank pages.)
So, to remove the problem, I then clear all tags on products.
With all tags cleared, I then go to a single product in "Categories/Products" and provide a title, desc and keyword and save that. The result is that this single product returns a blank page. To remove the tags on this one item I have to use the Clear All on the Fill Tags page.
Now, when I added your comment line to the includes/header_tags.php file, the title, desc and keyword did show up (all by themselves) and the remainder of the page is blank.
I hope I've straightened out any confusion I may have casused. Thanks for your help.