For some reason IE8/IE7/IE6/IE5 on Windows XP, instead to use the certificate that is listed on the nginx website config, is using another certificate that is used from other websites.

Checking the nging config file for the website everything is fine. A confirm of this is that all the other browsers (Chrome/Firefox/Safari/IE9) are using the correct certificate.

This is the nginx configuration for the app:

server {
listen 80;
listen 443 ssl;

server_name mydomain.com;
ssl_certificate /root/certs/mydomain.com/mydomain.bundle.crt;
ssl_certificate_key /root/certs/mydomain.com/mydoamin.key;

access_log /opt/webapps/cs_at/logs/access.log;

location / {
    add_header P3P 'CP="CAO PSA OUR"';
    proxy_pass http://127.0.0.1:20004;
    proxy_set_header Host $host;
    proxy_set_header X-Forwarded-For $remote_addr;
    proxy_set_header X-Real-IP $remote_addr;
}

}