I currently have both the Lumia 520 and 521. On my 521 (which is on T-Mobile), I have to re-enter my Wi-Fi password every single time that it's either locked, timed-out or restarted. To be honest, it just won't save. Has anyone else encountered this problem? I don't have this problem with my 520 and I think I've checked every single setting in my smartphone too. Any help would be appreciated.