Good thing I'm posting an install maintenance release in the morning. I'll have this fixed first thing... I thought I had grepped the code for any uses of old functions. You just need to change this:
<?php
if ($order === FALSE || $order->order_status != uc_get_order_status_id('in_checkout')) {
?>To this:
<?php
if ($order === FALSE || uc_order_status_data($order->order_status, 'state') != 'in_checkout') {
?>