When you create new row you've already binded editable to existing rows not the new one. You've got to bind editable to the new row.
Example: http://jsfiddle.net/9zP8k/
var row = $('<tr><td><a href="#" class="edit_text">Name Me</a></td><td> </td> </tr>');
$('.issue-table > tbody:last').append(row);
$('.edit_text').editable({
type: 'text',
title: 'Enter username'
});