On my site, I have external data list in my bdc store. For some reason, when I try to access my external list, I get a link telling me to "click here to authenticate." When I click there, I get a message about not using a certificate, and I click continue to site. After that I can authenticate using my domain admin account, but none of the accounts tied to sharepoint.
I needed to set my secure store application as a group type instead of individual. Problem solved.