If you've ever used Google ChatBack you know it's an excellent utility for chatting with web vistors.  However, if you're not using a standard gmail account i.e. standard or premium then you need to follow a different url to create the chatback badge.  That link is here http://www.google.com/talk/service/a/YOURDOMAIN.com/badge/New  You must substitute YOURDOMAIN with your custom domain name.  This will resolve the issue.