Just some thoughts for you…

When you go to Authors & Users I assume you see a list of users, one being you (admin), and then also client1 and client2. What is the ROLE that displays for these two users… is it subscriber? I usually assign subscriber (the lowest WP role) to all users, and use Role Scoper to increase what they can do. I'm not sure how Role Scoper will handle a user with "–No Role For This Blog–" assigned.

Now try going to Roles->Options->RS Role Definitions and at the very bottom of the screen check the box that says "Re-Sync with Wordpress roles in next update", then click the Update button underneath it.

Now go back to Roles->General and see what happens.