I have been trying without success to run SSL on more than one instance
at the same time.
You want to keep your standard and SSL configurations in the same file. One problem we've had with running multiple SSL instances is collision on SSLMutex and SSLSessionCache storage. Each instance should use a separate value for these directives.
http-server1.conf:
Listen x.x.x.1:80
<VirtualHost:x.x.x.1:80>
# your vhost stuff
</VirtualHost>
<IfModule mod_ssl.c>
Listen x.x.x.1:443
SSLEngine On
SSLSessionCache dbm:/var/run/ssl_scache-server1
SSLMutex file:/var/run/ssl_mutex-server1