I am unable to edit the tag on any of my product pages, however, I am able to edit on all other pages. The Page Title option or slot is not even shown on the edit of my products. I have the Page Title module (6.x-2.5) uploaded and enabled. Any ideas?
Page Title is enabled (or disabled) on a per content-type basis.
You should be able to go to http://mysite.com/admin/content/types/product and enable it using the checkbox in the following fieldset: