now let me explain a few things also.. saying it doesn't work isn't enough information. it is either not posting to it or not showing whats posted.
so I had you go make it accessible to admins and you were able to post to it and see it in the forum so its good there its just the script
now when you look at the shoutbox was what you say in the forum there? that could mean shoutdisplaypal.php was in err.. if you saw it then try and make a shout in the shoutbox and see if you can see it in the forum if you can't then that means shoutaddal.php could be in err... the last two pals, shoutdelpal.php just deletes a shout if your admin and shoutboxpal.php which assembles it all could also be in err but only in rare circumstances. I would mostly check the shoutadd and shoutdisplay pals.
