I've received many comments like this one from Shigeya Tanabe:
mmm.. This InfoCard auth looks like it's not working with March 20th version of IE7. It says â€œIE has blocked this website from displaying non-secure contentâ€. instead of prompting to download â€˜Microsoft Information Card IE Helperâ€™.
So please hold off on further testing until I resolve the state of this. I've had a really busy week what with the MIX06 conference and everything else. I'll post again over the weekend.