New KB article: You may receive a message in Internet Explorer 6 when you visit an IIS 6.0 Web site that uses a certificate from Microsoft Certificate Services
In Microsoft Internet Explorer 6, you visit a Microsoft Internet Information Services (IIS) 6.0 Web site that uses a certificate from Microsoft Certificate Services. When you do this, you may receive the following message:
Information you exchange with this site cannot be viewed or changed by others. However, there is a problem with the site's security certificate.
The security certificate was issued by a company you have not chosen to trust. View the certificate to determine whether you want to trust the certifying authority.