If you change lines 75 – 80 with what i have below, it will always show you what you have selected when you go back to the settings page. Granted this is a small patch for what was already there. We should really query the database and pull the list of user types from there.
<option value="" <?php if($opt_val == ''):?>selected="selected" <?php endif; ?>>No One</option>
<option value="administrator" <?php if($opt_val == 'administrator'):?>selected="selected" <?php endif; ?>>Administrators</option>
<option value="editor" <?php if($opt_val == 'editor'):?>selected="selected" <?php endif; ?>>Editors</option>
<option value="author" <?php if($opt_val == 'author'):?>selected="selected" <?php endif; ?>>Authors</option>
<option value="contributor" <?php if($opt_val == 'contributor'):?>selected="selected" <?php endif; ?>>Contributors</option>
<option value="subscriber" <?php if($opt_val == 'subscriber'):?>selected="selected" <?php endif; ?>>Subscribers</option>