Hi,
I was able to get this to work in vb 4.0.0 (mediawiki 1.14) by editing AuthPlugin_vBSSO.php by adding 3 chdir commands twhere the scripts are called
<<<<<
define('THIS_SCRIPT', 'wiki');
chdir ('/home/sitename/www/forums');
require_once( CWD . '/global.php');
chdir ('/home/sitename/www/forums');
require_once( CWD . '/includes/functions.php');
chdir ('/home/sitename/www/w/includes');
<<<<<
the second chdir is redundant, i think, but just to be safe.
so far working, but will see how stable it is.
ndahiya