Here's the other one:

The "collectsCardDataOnsite" interface changed between Zen Cart 1.5.4 and 1.5.5 and the plugin's using the 1.5.4 version (which was used to verify the authorizenet_aim payment method). Need to update /includes/modules/pages/checkout_one/jscript_main.php to include the ZC 1.5.5 version of the interface as well.

To correct, add the highlighted code sections:
Code:
function shippingIsBilling () 
{
    var shippingAddress = document.getElementById ('checkoutOneShipto');
    if (shippingAddress) {
        if (document.getElementById ('shipping_billing').checked) {
            shippingAddress.className = 'hiddenField';
            shippingAddress.setAttribute ('className', 'hiddenField'); 
        } else {
            shippingAddress.className = 'visibleField';
            shippingAddress.setAttribute ('className', 'visibleField');
        }
    }
}

<?php
// -----
// The "collectsCartDataOnsite" interface built into Zen Cart magically transformed between
// Zen Cart 1.5.4 and 1.5.5, so this module for the One-Page Checkout plugin includes both
// forms.  That way, if a payment module was written for 1.5.4 it'll work, ditto for those
// written for the 1.5.5 method.
// 
?>
function collectsCardDataOnsite(paymentValue)
{
    zcJS.ajax({
        url: "ajax.php?act=ajaxPayment&method=doesCollectsCardDataOnsite",
        data: {paymentValue: paymentValue}
    }).done(function( response ) {
        if (response.data == true) {
            var str = $('form[name="checkout_payment"]').serializeArray();

            zcJS.ajax({
                url: "ajax.php?act=ajaxPayment&method=prepareConfirmation",
                data: str
            }).done(function( response ) {
                $('#checkoutPayment').hide();
                $('#navBreadCrumb').html(response.breadCrumbHtml);
                $('#checkoutPayment').before(response.confirmationHtml);
                $(document).attr('title', response.pageTitle);

            });
        } else {
            zcLog2Console ('collectsCartDataOnsite: submitting form');
            $('form[name="checkout_payment"]')[0].submit();
        }
    });
    return false;
}

function doesCollectsCardDataOnsite(paymentValue)
{
    if ($('#'+paymentValue+'_collects_onsite').val()) {
        if ($('#pmt-'+paymentValue).is(':checked')) {
            return true;
        }
    }
    return false;
}

function doCollectsCardDataOnsite(paymentValue)
{
    var str = $('form[name="checkout_payment"]').serializeArray();

    zcJS.ajax({
        url: "ajax.php?act=ajaxPayment&method=prepareConfirmation",
        data: str
    }).done(function( response ) {
        $('#checkoutPayment').hide();
        $('#navBreadCrumb').html(response.breadCrumbHtml);
        $('#checkoutPayment').before(response.confirmationHtml);
        $(document).attr('title', response.pageTitle);
    });
}