Microsoft Knowledge Base Article 870700 contains the following introduction:

After you upgrade to Microsoft Internet Explorer 6.0 Service Pack 2 (SP2) in Microsoft Windows XP SP2, some SSL-secured (128-Bit) Web pages and Web sites may not work correctly. Frequently, this behavior is caused by security changes in Windows XP SP2. To determine why the pages do not display correctly, use the following methods in the order that they are presented.