On the Domain Mapping plugin, when I select to exclude

On the Domain Mapping plugin, when I select to exclude a checkout page /checkout, so that the person is instead sent to the subdomain, it just redirects back and forth until it times out.

So for example, if I go here when I have selected to exclude the page:

http://www.demo-blog.com/checkout/

You will see the browser bouncing between that url and demo-blog.websiteplushosting.com/checkout/