So I've figured out that this is due to having installed an SSL certificate on the website. The call to http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js
is not secure, so it's not loading.
The only reference I can find to this file is in "ajaxupload.html" which is in the core/packages/migx-2.9.6-pl/ folder. But when I update that to https
://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js the change isn't occurring and the error still appears (even after clearing core/cache and my browser cache etc).
Any thoughts on how to update that path to be secure would be much appreciated.