certificate's CN name does not match the passed value

My friend is getting the following message when starting up OE:

Internet Security Warning
The server you are connected to is using a security certificate that could
not be verified.
The certificate's CN name does not match the passed value.
Do you want to continue using this server?
Yes No

I looked at the security certificates on my own system. In Outlook
Express, I selected Tools - Options - Security - Digital IDs. The
Certificates dialog shows a list certificates under several tabs: Personal,
Other People, Intermediate Certification Authorities, Trusted Root
Certification Authorities, Trusted Publishers, Untrusted Publishers.

On my system, I have well over 100 certificates listed in these tabs! How
do I know which certificate is causing the problem?