Solved it!!!!!!!!!!!
My issues were multiple:
WPPoll utilizes AJAX for storing data, and as such, required access to /wp-admin/admin-ajax.php. This was disabled by selecting (checking) "Prevent Subscribers Access to the WordPress Admin" in the Mingle plug-in settings. When this was unchecked, WPPoll began functioning as expected, but this left the ability for Subscribers to get to the Dashboard.
To override this, it is necessary to add a few lines of code to the functions.php file in your theme to allow access to admin-ajax.php, but nothing else.
add_action( 'admin_init', 'blockusers_init' );
function blockusers_init() {
if (! is_super_admin() && $_SERVER['PHP_SELF'] != '/wp-admin/admin-ajax.php' ) {
wp_redirect( home_url() ); exit;
}
}
This will cause any requests into /wp-admin/ to be redirected to the home page if the user is not logged in as an administrator.
Note: Make sure that if your site is not in the root of your domain (e.g. http://www.somesiteurl.net/something/), you will need to add the appropriate directory(ies) to the beginning of the /wp-admin/admin-ajax.php path.
Now the code will run and the directory is not easily accessible.