Gallery dropping item id in url

Hi, I have had gallery going for a few months with no probs, very happy with it, but i have somehow created a problem where the gallery url is dropping the item id (46) and so it will say (if u try to click on an album) 'you are not authorised to view this resource, you must login' .

Example-
http://halcyondaze.info/index.php?set_albumName=fiji-shotz&option=com_gallery&Itemid=&include=view_album.php

<You are not authorized to view this resource.
You need to login.>

But if I add the item id in to that same url, like so-
http://halcyondaze.info/index.php?set_albumName=fiji-shotz&option=com_gallery&Itemid=46&include=view_album.php

It then works fine for guests... So why is mambo taking off the item id? And how can i fix it?

Any ideas?

thanks