Submitting ideas does SAML redirect to insecure site.
The new topic button on your secure web site redirects to http://ideas.travelingmailbox.com/topic/add , which is insecure. Of course, the browser prompts for an exception. Is there any reason this needs to be an insecure link?
Accessing the address as https shows that you don't have a certificate for the ideas... domain. Get one? Use a wildcard certificate for *.travelingmailbox.com?