MailChimp Embed Not Showing Success Response

This is making me crazy. I don’t want to use a plugin for my newsletter sign-up form– just the regular “embed” code MailChimp provides. I put it in the body in header.php.

When the email address I enter is not valid I get a proper error message. However, when the email is valid, I get no success message. The confirmation email is sent, so the form is actually submitting properly. Here is the code (minus the account details, replaced with “private”):

<!-- Begin MailChimp Signup Form -->

<script type="text/javascript">
// delete this script tag and use a "div.mce_inline_error{ XXX !important}" selector
// or fill this in and it will be inlined when errors are generated
var mc_custom_error_style = '';
</script>
<div id="mc_embed_signup">
<form action="private" method="post" id="mc-embedded-subscribe-form" name="mc-embedded-subscribe-form" class="validate" target="_blank">
	<fieldset>
<div class="mc-field-group">
<input type="text" value="enter your email address" name="EMAIL" class="required email" id="mce-EMAIL" />
</div>

		<div>
	             <input type="submit" value="submit" id="submit" name="subscribe" id="mc-embedded-subscribe" class="btn" /></div>
		<div id="mce-responses">
		<div class="response" id="mce-error-response" style="display:none"></div>
		<div class="response" id="mce-success-response" style="display:none"></div>
		</div>
</fieldset>
</form>
</div>

<script type="text/javascript">
var fnames = new Array();var ftypes = new Array();fnames[0]='EMAIL';ftypes[0]='email';fnames[1]='FNAME';ftypes[1]='text';fnames[2]='LNAME';ftypes[2]='text';fnames[3]='MMERGE3';ftypes[3]='birthday';fnames[4]='MMERGE4';ftypes[4]='url';
try {
    var jqueryLoaded=jQuery;
    jqueryLoaded=true;
} catch(err) {
    var jqueryLoaded=false;
}
var head= document.getElementsByTagName('head')[0];
if (!jqueryLoaded) {
    var script = document.createElement('script');
    script.type = 'text/javascript';
    script.src = 'http://ajax.googleapis.com/ajax/libs/jquery/1.4.4/jquery.min.js';
    head.appendChild(script);
    if (script.readyState && script.onload!==null){
        script.onreadystatechange= function () {
              if (this.readyState == 'complete') mce_preload_check();
        }
    }
}
var script = document.createElement('script');
script.type = 'text/javascript';
script.src = 'http://downloads.mailchimp.com/js/jquery.form-n-validate.js';
head.appendChild(script);
var err_style = '';
try{
    err_style = mc_custom_error_style;
} catch(e){
    err_style = '';
}
var head= document.getElementsByTagName('head')[0];
var style= document.createElement('style');
style.type= 'text/css';
if (style.styleSheet) {
  style.styleSheet.cssText = '.mce_inline_error {' + err_style + '}';
} else {
  style.appendChild(document.createTextNode('.mce_inline_error {' + err_style + '}'));
}
head.appendChild(style);
setTimeout('mce_preload_check();', 250);

var mce_preload_checks = 0;
function mce_preload_check(){
    if (mce_preload_checks>40) return;
    mce_preload_checks++;
    try {
        var jqueryLoaded=jQuery;
    } catch(err) {
        setTimeout('mce_preload_check();', 250);
        return;
    }
    try {
        var validatorLoaded=jQuery("#fake-form").validate({});
    } catch(err) {
        setTimeout('mce_preload_check();', 250);
        return;
    }
    mce_init_form();
}
function mce_init_form(){
    jQuery(document).ready( function($) {
      var options = { errorClass: 'mce_inline_error', errorElement: 'div', onkeyup: function(){}, onfocusout:function(){}, onblur:function(){}  };
      var mce_validator = $("#mc-embedded-subscribe-form").validate(options);
      $("#mc-embedded-subscribe-form").unbind('submit');//remove the validator so we can get into beforeSubmit on the ajaxform, which then calls the validator
      options = { url: 'private', type: 'GET', dataType: 'json', contentType: "application/json; charset=utf-8",
                    beforeSubmit: function(){
                        $('#mce_tmp_error_msg').remove();
                        $('.datefield','#mc_embed_signup').each(
                            function(){
                                var txt = 'filled';
                                var fields = new Array();
                                var i = 0;
                                $(':text', this).each(
                                    function(){
                                        fields[i] = this;
                                        i++;
                                    });
                                $(':hidden', this).each(
                                    function(){
                                        if (fields.length == 2) fields[2] = {'value':1970};//trick birthdays into having years
                                    	if ( fields[0].value=='MM' && fields[1].value=='DD' && fields[2].value=='YYYY' ){
                                    		this.value = '';
									    } else if ( fields[0].value=='' && fields[1].value=='' && fields[2].value=='' ){
                                    		this.value = '';
									    } else {
	                                        this.value = fields[0].value+'/'+fields[1].value+'/'+fields[2].value;
	                                    }
                                    });
                            });
                        return mce_validator.form();
                    },
                    success: mce_success_cb
                };
      $('#mc-embedded-subscribe-form').ajaxForm(options);      

    });
}
function mce_success_cb(resp){
    $('#mce-success-response').hide();
    $('#mce-error-response').hide();

    if (resp.result=="success"){
        $('#mce-'+resp.result+'-response').show();
        $('#mce-'+resp.result+'-response').html(resp.msg);
        $('#mc-embedded-subscribe-form').each(function(){
            this.reset();
    	});
    } else {
        var index = -1;
        var msg;
        try {
            var parts = resp.msg.split(' - ',2);
            if (parts[1]==undefined){
                msg = resp.msg;
            } else {
                i = parseInt(parts[0]);
                if (i.toString() == parts[0]){
                    index = parts[0];
                    msg = parts[1];
                } else {
                    index = -1;
                    msg = resp.msg;
                }
            }
        } catch(e){
            index = -1;
            msg = resp.msg;
        }
        try{
            if (index== -1){
                $('#mce-'+resp.result+'-response').show();
                $('#mce-'+resp.result+'-response').html(msg);
            } else {
                err_id = 'mce_tmp_error_msg';
                html = '<div id="'+err_id+'" style="'+err_style+'"> '+msg+'</div>';

                var input_id = '#mc_embed_signup';
                var f = $(input_id);
                if (ftypes[index]=='address'){
                    input_id = '#mce-'+fnames[index]+'-addr1';
                    f = $(input_id).parent().parent().get(0);
                } else if (ftypes[index]=='date'){
                    input_id = '#mce-'+fnames[index]+'-month';
                    f = $(input_id).parent().parent().get(0);
                } else {
                    input_id = '#mce-'+fnames[index];
                    f = $().parent(input_id).get(0);
                }
                if (f){
                    $(f).append(html);
                    $(input_id).focus();
                } else {
                    $('#mce-'+resp.result+'-response').show();
                    $('#mce-'+resp.result+'-response').html(msg);
                }
            }
        } catch(e){
            $('#mce-'+resp.result+'-response').show();
            $('#mce-'+resp.result+'-response').html(msg);
        }
    }
}

</script>
<!--End mc_embed_signup-->

When I submit a correct email address, the error message I get is that #mce-success-response is null.