As far as I have tested on my website everything still works after this change.
Hi,
found solution. The needed change needed is in the plugin Polylang.
in polylang/frontend/frontend-links.php change
add_action('wp', array(&$this, 'check_canonical_url'), 10, 0); // before WordPress redirect_canonical, avoid passing the WP object
to
add_action('wp', array(&$this, 'template_redirect'), 10, 0); // before WordPress redirect_canonical, avoid passing the WP object
This works on PolyLang 1.7.6 and NextGEN 2.1.0.
