I've had creaks from most parts of a Dahon. The handlepost clamp, the main hinge, the seatpost shim against the interior of the frame. On my Vitesse I had to keep the entire surface area of the main hinge plates greased. The powdercoat quickly wore through on parts of the contact areas and there's bare aluminium touching; almost guaranteed to creak. The interior of the frame against the exterior of the seat post shim is also aluminium on aluminium; worth greasing, taking care to avoid getting any on the interior of the shim.