Looking at the error I'd want to see <?php include('/linkmanager/links.php'); ?> PHP: changed to <?php include('/home/notting/public_html/linkmanager/links.php'); ?> PHP: BUT that page also has <html><body> tags (etc) in it so will not necessarily display properly. I'd make a separate version of it with just the text. I've never encountered that. Single and Double just give a different command to PHP on how to handle the string. That should be done before the include gets it...
I had mentioned your above a few times for full path. I think hes getting lost in all the posts. the single and double quotes for some reason in some scripts to have a certain type of effect. not sure why. I just know in my experiences with how some scripts handle the include statement and php processes the command it tends to need it one or the other.