Are you still having a problem with it? I tried creating a plugin using parse_templates with that code, and I created a template called ratemysite_headinclude with the code you posted, and it works for me (I didn't use a product xml file so I can't say that the xml you posted is exactly right).
Did you check the html source of a page to see if anything is there?
Strange.... very strange... Yes, I'm sure for the code... I also cleared many times the cached. Also, except reading the page's output code, I used the search to find any of the script names. Nothing.
In any case thank you both for your help. I already released my mod yesterday, and I believe that is not good to add this plugin as will confuse the members who already manually added those links.