Lid,
The error message means that you have an element in your document with no content but is required to contain one or more entry elements. You are working with a table, and entry is a common element tag for table cells. Without knowing more about the template you are using, I can't be sure, but my first guess is that the erroneous element is a row that is supposed to contain at least one cell but does not. This situation can occur when all cells in a row are straddled from rows above or if the table was created by using a conversion table when there are hidden conditional rows.
To investigate, open the Structure View. Then use the Structure > Validate command in FM 2017 or Element > Validate in earlier versions to validate the document. The Structure View will show you the element with the problem; you may need to expand one or more elements to locate the error precisely. If you do indeed see an empty row, use the Table > Unstraddle command in at least one cell in the preceding row. That will make an entry appear in the empty row and you will be able to delete the row.
If entry is not the element tag for your table cells, validating the document will still locate the problem.
--Lynne