We just don't have the necessary info to help with most Smashwords' meatgrinder errors—except in the most generic way. The error itself means that there's something wrong with the value of the CLASS attribute of an html tag near line 20. The problem is... you're not writing html. You only have a Word Document to work with. You don't have access to the file that has the bad class value in it, because it's a temporary file that the meatgrinder creates as an intermediate step on its way to becoming an epub.