Hi!
When you look at your template in Auctiva after pasting in the html code, switch over to "Design Editor". In this view, you will see what your template will look like on auctiva. See where it says "Type Your Description Here"? You need to replace that with the descrition tag that auctiva uses. Basically highlight that by dragging your mouse and then replace it by clicking on where it says "Description" in the left hand margin. I just tried it and saved it and it worked (no errors).
I just had a template made it too but had to insert some tags. You can also do the same for pictures so that you do not have to insert the URLs into your html. You just set up the auctiva tags and then you can choose your images through the listing page on Auctiva. The same can be said for your terms of sale as there are tags for those too.
If you have more questions (I am not always clear) please feel free to ask for more help!
Marcia