jQuery doesn't add or remove class
<p>Why doesn't my jQuery code add and later remove loading class?</p>

<pre><code>$('#crop').click(function (ev) {
    ev.preventDefault()
    $.post('frame.php?action=crop', dimensions, function (json) {
        $('body').addClass('loading')
        picture()
    }, 'json')
    $('body').removeClass('loading')
})
</code></pre>

<p>Chrome and Firebug consoles are empty, so there shouldn't be any errors.
jQuery version is 1.4.4</p>
