Version appears to break SSO based logins

We've updated to v1.1.8.4 (from our users that authenticate via the SSO (Shibboleth)are redirected to wp-login.php to login instead of back to the actual site (ie, browse to WP then redirects them to the SSO authentication but are then redirect to wp-login.php that require another login). Previous version wouldn't require this additional login.

Our network sites are set to 'Only allowed logged in users to see all sites' and we are using the Shibbolize plugin for SSO authentication.

Note: We have another network site setup identical to the one that is broken except that its running I'll be downgrading the plugin to from until this is fixed.