Help needed! SSL certificate replaced, but site delivers old one still?!

I have only one web site that uses SSL. The old certificate is still valid for two weeks, but I decided to replace it with a new certificate from another CA (due to payment issues with the old CA). I followed the Microsoft KB article "How To Renew or Create New Certificate Signing Request While Another Certificate Is Currently Installed" (http://support.microsoft.com/kb/295281), and replaced the certificate successfully. However when I browse to a web site from a browser, the certificate delivered by the site is the old certificate. This worries me, as the certificate goes out of date in two weeks. I have started and stopped the SSL web site. I have restarted IIS completely. I have verified that the new certificate hash is correct in the IIS metabase and that it is the only certificate hash in the metabase. I can't figure out why the certificate displayed is the old one despite the fact that the web site does no longer use it in the IIS manager. Can anyone tell me how I can fix this?