Database Error - nodeaccess_author duplicate entry

This is a great module. Exactly what I needed! However, I'm having a tough time setting permissions properly and so perhaps I just need a primer.

Use case:
I'm using only two content types "Basic" and "Private". All the basic nodes are created by admin and I want visible (VIEW ONLY) to the world. All private nodes are created by individual users and I want them to manage grants to individual user only for VIEW ONLY access and not by role. I only want the "View" - Allowed grants available to these node authors. I'm not using any other node type access module, unless you count Drupal's default.

If I understand the readme file correctly, once this module is enabled all nodes permissions will be handled by this module? So, I don't need to be concerned with any of the Drupal default settings for Node permissions in admin/people/permissions?

I'm hoping I've given enough info for you to basically tell me what boxes to check in each section of the nodeaccess settings page to make my use case work.

Below is the error I keep getting after trying to save a node.

PDOException: SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '1-1-nodeaccess_author' for key 'PRIMARY': INSERT INTO {node_access} (nid, realm, gid, grant_view, grant_update, grant_delete) VALUES (:db_insert_placeholder_0, :db_insert_placeholder_1, :db_insert_placeholder_2, :db_insert_placeholder_3, :db_insert_placeholder_4, :db_insert_placeholder_5), (:db_insert_placeholder_6, :db_insert_placeholder_7, :db_insert_placeholder_8, :db_insert_placeholder_9, :db_insert_placeholder_10, :db_insert_placeholder_11); Array ( [:db_insert_placeholder_0] => 1 [:db_insert_placeholder_1] => nodeaccess_author [:db_insert_placeholder_2] => 1 [:db_insert_placeholder_3] => 1 [:db_insert_placeholder_4] => 1 [:db_insert_placeholder_5] => 1 [:db_insert_placeholder_6] => 1 [:db_insert_placeholder_7] => nodeaccess_author [:db_insert_placeholder_8] => 1 [:db_insert_placeholder_9] => 1 [:db_insert_placeholder_10] => 1 [:db_insert_placeholder_11] => 1 ) in node_access_write_grants() (line 3564 of /home/xxx/public_html/xxx/modules/node/node.module).

Thank you in advance for any assistance!

Mark