jQueryUI modal dialog does not show close button (x)

I'm using a jQuery modal dialog in my ASP .NET MVC 3 application. It works fine except for that there is no close button showing in the top right corner. How can I add this?

$("#dialog-modal").dialog({
            modal: true,
            autoOpen: false,
            buttons: {
                Ok: function () {
                    $(this).dialog("close");
                }
            }
        });

Another possibility is that you have the bootstrap library. Some version of bootstrap and jquery-ui have conflict with the .button() method, and if your bootstrap.js is placed after jquery-ui.js, the bootstrap .button() overrides your jquery button and the jquery-ui 'X' image would then not show up.

see here: https://github.com/twbs/bootstrap/issues/6094

This works (close box visible):

<script src="//netdna.bootstrapcdn.com/twitter-bootstrap/2.3.2/js/bootstrap.min.js"></script>
<script src="//ajax.googleapis.com/ajax/libs/jqueryui/1.10.3/jquery-ui.min.js"></script>

This causes the issue:

<script src="//ajax.googleapis.com/ajax/libs/jqueryui/1.10.3/jquery-ui.min.js"></script>
<script src="//netdna.bootstrapcdn.com/twitter-bootstrap/2.3.2/js/bootstrap.min.js"></script>

I had this problem and was able to resolve it with the declaration below.

$.fn.bootstrapBtn = $.fn.button.noConflict();

In the upper right corner of the dialog, mouse over where the button should be, and see rather or not you get some effect (the button hover). Try clicking it and seeing if it closes. If it does close, then you're just missing your image sprites that came with your package download.