I had the SSL Certificate expire on an older SME Server install during the week and went to fix it all this morning. I went looking for a quick set of instructions and used http://www.sme-server.de/download/Howtos/ssl.html which worked fine on the server.

Problem was that the Firefox browser on the workstation I worked from reported a duplicate certificate serial number had been identified and therefore the site was still blocked.

I had to clear the old certificate from the Tools->Options->Advanced->Encryption->View Certificates screen to get access working.