This is an older plugin now and hasn't been updated to work around newer WordPress additions. One such addition is the nav_menu_item post_type, and it ends up trying to validate them.
To fix this, open up toptions.php and change line 14 to this:
$myQuery="SELECT ID,post_name,guid FROM " . $prefix . "posts WHERE post_status='publish' AND post_type!='nav_menu_item' ";
Hopefully this could get implemented into a future version, if the plugin developer is still among the living.
