[jQuery] ajaxForm returns error in IE7

[cjokomay]

I am using ajaxForm to upload an excel file and then display whether
or not it uploaded successfully. The following jQuery code works fine
in Firefox, but when I try to run it in IE7 it fails. The beforeSubmit
function is executed but then it craps out after that with the
following error: "Object doesn't support this property or method." The
form is generated dynamically, hence the reason for livequery.

$("#taskplans form.upload-form").livequery(function() {
        var h3 = $("#taskplans h3");
        var content = $("#taskplans div.content");

        $(this).ajaxForm({
                beforeSubmit: function() {
                        h3.append(" " + loaderImg);
                },
                error: function(data) {
                        h3.find("img").remove();
                        content.html(data);
                },
                success: function(data) {
                        h3.find("img").remove();
                        content.html(data);
                }
        });
});