Enterprise Root Certificate Authority and Certificates

When I installed Windows Enterprise 2003 about a year ago, I imported a
certificate from my Small Business Server 2003 and all my web sites worked
fine. I wanted to implement RPC over HTTP for MS Exchange and Outlook and
found that I should install a CA. I installed the CA and replaced my current
certificate (I did export it first). Now, even though my web sites require
SSL, the browser states that the Web page can't be displayed. When I uncheck
the SSL requirement, and type in http:// instead of https:// the web site
works. I don't know what to do now and need to fix this fast! Any/All your
assistance is greatly appreciated!
Thanks.

JoeF