Hey Josh,
Please try a different browser (like firefox or chrome) if you're on IE.
Else try to login with a different page access such as:
http://<IP of your ESA>/mail_policies/email_security_manager/incoming_mail_policies
And see if that lets you in, and you may need to remove any previous bookmarks if it is within a page which is no longer available on the ESA.
Regards,
Matthew