I have a strange bug. One invoice gives as owing amount (on the invoice overview/manage page): 2.8421709430404e-14 It seems that there is some king of rounding problem but can't find where. In the modules/invoice/manage.php the value is 0, it seems smarty is giving some problems here.
"|number_format:2" in this line solves the problem but it shouldn't be needed. Line 115: <td class="index_table">{$invoice.owing|number_format:2}</td>