Hi agujoa,
In that case, it seems the issue has to do with how you're using the addin. It's not something I've used, so I can't give any specific advice. You could, of course, ask Mr Mayor, from whose site you obtained the addin. There's an email feedback link on this page:
http://www.gmayor.com/index.htm
I did notice that your attachment had a Section break at the bottom of the page. If that's indicative of your mailmerge main document's content, that might be part of the issue.