I tried to update mine to NBG-416N_V1.00(USA.4)C0 and BRICKED. Seeing you post, trying to download the NBG416N_recover_kit.zip kit, but only downloads 184k file and not the 2.4Mb file.... not sure what is going on.
Tried google/zyxel for this file and cannot get it anywhere else. HELP...!! any other place that I can get this file from?