Actually I just tried it on my test site with the document code and it worked fine, with only 1 product description. I was wrong about the class thing. TPP actually uses the id, which is the same in all display files so there are no changes needed for TPP.
(outsmarted myself :) )
Try my version of the file and see if it works.
Also what is your setting for the "Global Product Description Tab"?
Are you using any custom tag codes?
Bookmarks