SSL No Longer Works when Existing Certificate is Installed

I have a seemingly simple issue that I cannot figure out.

I am running a website using IIS 6 with an SQL Server 2000 backend on
Windows Server 2003 Standard Edition. Using the SelfSSL tool that is part
of the IIS 6 Resource Kit I am able to generate a self-signing ssl
certificate without issue. I am also able to use several older certificates
that either coorespond to older systems or to a previous instance of the
said server.

When I attempt to install a valid certificate issued by Thawte the SSL
portion of the website stops responding altogether. I keep
getting "Connection Interrupted" or similar messages from clients
connecting to the website. I have restarted the server everytime I
installed a certificate to attempt to see if there was an conflict with an
item resident in memory.

Is there anything that I have not looked at or need to do? Thank you in
advance.

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Regards,

Christopher Kurtis Koeber