Getting modal to dynamically resize when window is resized

I've managed to get my Block UI modal dead centre but now the problem is that when the window is resized (made smaller or bigger), the modal (and the surrounding overlay) does not dynamically resize. Is there a way I can achieve this using jQuery? Here is what I've done so far: http://jsfiddle.net/2dpc7/. If you try dragging the Results panes then you can see that the modal doesn't really dynamically adjust to fit. Why is this?

HTML

<div style="float: left;">
        <a id="about" class="windowClass" href="#">About</a>&nbsp;&middot;
        <a id="terms" class="windowClass" href="#">Terms</a>&nbsp;&middot;
        <a id="privacy" class="windowClass" href="#">Privacy</a>&nbsp;&middot;
        <a id="language" class="windowClass" href="#">Language: English</a>
</div>
<div id="register_win" class="modal">
    <span class="modal_header">Register</span>
    <div class="modal_close">
        <img src="http://www.ezpz.co.za/assets/close-button-25f4a789916c34b8c927d7d0ec98410b.gif" id="register_close">
    </div>
</div>
<div id="about_win" class="modal">
    <span class="modal_header">About</span>
    <div class="modal_close">
        <img src="http://www.ezpz.co.za/assets/close-button-25f4a789916c34b8c927d7d0ec98410b.gif" id="about_close">
    </div>
</div>
<div id="terms_win" class="modal">
    <span class="modal_header">Terms</span>
    <div class="modal_close">
        <img src="http://www.ezpz.co.za/assets/close-button-25f4a789916c34b8c927d7d0ec98410b.gif" id="terms_close">
    </div>
</div>
<div id="privacy_win" class="modal">
    <span class="modal_header">Privacy</span>
    <div class="modal_close">
        <img src="http://www.ezpz.co.za/assets/close-button-25f4a789916c34b8c927d7d0ec98410b.gif" id="privacy_close">
    </div>
</div>
<div id="forgotpwd_win" class="modal">
    <span class="modal_header">Forgotten your password?</span>
    <div class="modal_close">
        <img src="http://www.ezpz.co.za/assets/close-button-25f4a789916c34b8c927d7d0ec98410b.gif" id="forgotpwd_close">
    </div>
</div>
<div id="language_win" class="modal">
    <span class="modal_header">Language</span>
    <div class="modal_close">
        <img src="http://www.ezpz.co.za/assets/close-button-25f4a789916c34b8c927d7d0ec98410b.gif" id="language_close">
    </div>
</div>

CSS​

.modal {
    display: none;
    padding: 10px;
    cursor: default;
}
.modal_header {
    font-family: Verdana, Geneva, sans-serif;
    float: left;
}
.modal_close {
    cursor: pointer;
    float: right;
}​

JS

$(document).ready(function () {

    $('.windowClass').click(function () { // <-- bind to all window elements with that class
        $.blockUI({
            message: $('#' + this.id + '_win'),
            css: {
                top:  ($(window).height() - 200) /2 + 'px', 
                left: ($(window).width() - 200) /2 + 'px', 
                width: '200px'
            }
        });
    });

    $('[id$=_close]').click(function () { //<-- gets all elements with id's that end with close
        $.unblockUI();
        return false;
    });

});​

On the window.resize event you can re-position the element:

$(window).on('resize', function () {
    $('body').children('.blockMsg').css({
        top  : ($(window).height() - 40) /2 + 'px', 
        left : ($(window).width() - 200) /2 + 'px'
    });
});​

Here is a demo: http://jsfiddle.net/2dpc7/2/

This will find any current blockUI modals and update their top/left CSS properties to keep them centered.