[jQuery] Form Plugin Won't Work in IE

[AJ]

I've recently started using the form.js plugin (http://www.malsup.com/
jquery/form/) and I like it a lot. Except, I can't seem to get it
working right in IE (6 or 7).

Here is my code:

/* CODE -----------------------------------

function postloading() {
        // beforesubmit code goes here
        return true;
}
function postsuccess(data) {
        //success code goes here
        return true;
}
    $(".replyform").submit(function() {
    $(this).ajaxSubmit({
        dataType: 'json',
        type: 'POST',
        beforeSubmit: postloading,
        success: postsuccess
        });
        return false;
    });

 / CODE ------------------------------------*/

This worked perfectly in Firefox from the beginning. I've tried it
every way I can think of, and IE won't work. When the submit button is
clicked, the 'beforeSubmit' runs, and the form does get submitted (ie,
content is saved to the database, etc).

It just appears the 'success' callback is not firing. I've tried
simplifying it down to a simple alert('test'), but it just will not
fire.

Hoping someone has seen this sort of thing before. Thanks.