doesn't work if in path containing 'admin'

I've been banging my head against a wall trying to work out why I just get empty space where the editor should be on one of my sites - it works fine on all the others - and found that if I put the fckeditor folder inside a folder called admin, it doesnt work!

My test PHP file is:

<?
include("../fckeditor/fckeditor.php") ;
$oFCKeditor = new FCKeditor('FCKeditor1') ;
$oFCKeditor->BasePath    = "/vtt/admin/fckeditor/" ;
$oFCKeditor->Value        = 'This is some <strong>sample text</strong>. You are using <a href="<a href="http://www.fckeditor.net/" target="_blank">http://www.fckeditor.net/</a>">FCKeditor</a>.' ;
$oFCKeditor->Create() ;
?>

and fckeditor is in /vtt/admin/fckeditor/

This doesnt work.

But this:

<?
include("../fckeditor/fckeditor.php") ;
$oFCKeditor = new FCKeditor('FCKeditor1') ;
$oFCKeditor->BasePath    = "/vtt/admin2/fckeditor/" ;
$oFCKeditor->Value        = 'This is some <strong>sample text</strong>. You are using <a href="<a href="http://www.fckeditor.net/" target="_blank">http://www.fckeditor.net/</a>">FCKeditor</a>.' ;
$oFCKeditor->Create() ;
?>

in the folder

/vtt/admin2/fckeditor/

DOES work!

Any ideas?

cheers