Trouble with admin login on initial install

I did a fresh install of Zen Cart. I already have a dedicated SSL certificate, so I wanted to change the settings to allow SSL on checkout and on admin login.

In the configure.php files, there were the following lines of codes:

1. includes/configure.php

define('HTTP_SERVER', 'http://MYDOMAIN.com');
define('HTTPS_SERVER', 'https://MYDOMAIN.com');

// Use secure webserver for checkout procedure?
define('ENABLE_SSL', 'false');

2. admin/includes/configure.php

define('HTTP_SERVER', 'http://MYDOMAIN.com');
define('HTTPS_SERVER', 'https://MYDOMAIN.com');
define('HTTP_CATALOG_SERVER', 'http://MYDOMAIN.com');
define('HTTPS_CATALOG_SERVER', 'https://MYDOMAIN.com');

// Use secure webserver for catalog module and/or admin areas?
define('ENABLE_SSL_CATALOG', 'false');
define('ENABLE_SSL_ADMIN', 'false');

My SSl certificate is for https://www.MYDOMAIN.com, so I changed the codes as follows:

1. includes/configure.php

define('HTTP_SERVER', 'http://**www.**MYDOMAIN.com');
define('HTTPS_SERVER', 'https://**www.**MYDOMAIN.com');

// Use secure webserver for checkout procedure?
define('ENABLE_SSL', 'true');

2. admin/includes/configure.php

define('HTTP_SERVER', 'http://**www.**MYDOMAIN.com');
define('HTTPS_SERVER', 'https://**www.**MYDOMAIN.com');
define('HTTP_CATALOG_SERVER', 'http://**www.**MYDOMAIN.com');
define('HTTPS_CATALOG_SERVER', 'https://**www.**MYDOMAIN.com');

// Use secure webserver for catalog module and/or admin areas?
define('ENABLE_SSL_CATALOG', 'true');
define('ENABLE_SSL_ADMIN', 'true');

Everything in bold is what I changed or added.

When I go to my admin login page, I'm correctly directed to my https URL. However, when I actually login, the page blinks and nothing happens. It essentially refreshes itself.

I then changed everything back to the original settings, and everything works fine. So I have two questions:

1. Why couldn't I login in with the changes I made?

2. How do I make the cart go to https://www.MYDOMAIN.com when someone enters only MYDOMAIN.com? My SSL certificate requires the www prefix.

Again, this is a completely fresh install. I haven't changed any other settings other than changing my password.

I forgot to add that I did the initial install to a subdirectory:

http://www.MYDOMAIN.com/SOMEFOLDER/

I did this because I'm constructing Zen Cart while I phase out my current shopping cart. I'd like to clear up the SSL issue before proceeding forward. Any thoughts?

I seemed to got it working by configuring the two configure.php files as follows:

1. includes/configure.php

define('HTTP_SERVER', 'http://www.MYDOMAIN.com');
define('HTTPS_SERVER', 'https://www.MYDOMAIN.com');

// Use secure webserver for checkout procedure?
define('ENABLE_SSL', 'true');

2. admin/includes/configure.php

define('HTTP_SERVER', 'http://MYDOMAIN.com');
define('HTTPS_SERVER', 'https://www.MYDOMAIN.com');
define('HTTP_CATALOG_SERVER', 'http://MYDOMAIN.com');
define('HTTPS_CATALOG_SERVER', 'https://www.MYDOMAIN.com');

// Use secure webserver for catalog module and/or admin areas?
define('ENABLE_SSL_CATALOG', 'true');
define('ENABLE_SSL_ADMIN', 'true');

Does anyone know if this will pose a problem later on?

Everything should match when setup correctly ...