New SSL cert

I have this weird problem on a IIS6.0: I've recently installed a new SSL
certificate and although there is no problem in the IIS config, when I client
connects to the web server, IE still reports the use of the old certificate.
i've already removed the old certificate form the server, re-imported the
newer one and re-assigned it to the website... when I click 'view
certificate' it does display the new certificate valid untill 2008, yet when
I connect to the site through IE, I still get the certificate valid until
2006 !!

I've restarted the server, not a solution
Did an IIS reset several times, still the same
Checked the SSLhash in the IIS Metabase and compared to the Thumbprint of my
new certificate, they are identical !

Also imported the certificate on another server and linked it to a temporary
website, works fine.. Yet on my production server It keeps telling my browser
it had an SSL cert valid till 2006 instead of the 2008 cert !!

any help appriciated...

IIS 6.0 on a 2003 Std server (non SP1, yet all critical security patches
installed)

Nicolas