OK, a little more beating my head against the wall and I think I realized what the last error was saying.
I think that basically I had two different methods of doing the same thing...ISPConfig creates the virtual hosts in the /etc/apache2/vhosts/vhosts_ispconfig.conf file. I then used the method in the second web link (the debuntu.org one) to create virtual host conf files in the /etc/apache2/sites-available.
As a result, it was two methods of doing the same thing, sound reasonable?
I noticed that in the Apache section of webmin (which is also installed) the virtual hosts I had created were listed twice, removing my entries seems to have resulted in them only being listed once, and the error I listed in the last post being eliminated.
Unfortunately, I am also right back where I started, with the virtual hosts not working again. Entering the IP directly or typing any of the domains just lists the contents of /var/www.
There must be something is ISPConfig I am missing?