IE 4.x may damage the private key when a certificate is imported from a .pfx file.

When you attempt to log on to a secure site using the damaged certificate, you receive:

        title:- Microsoft Internet Explorer                                      Internet Explorer cannot open the internet site                                      https://.......                                      An error occurred in the secure channel support.
You must delete the damaged certificate and obtain a new one.

Microsoft recommends that you upgrade to IE 5.x and/or apply SP6a (or later) to prevent the problem from reoccurring.