I think there's a problem on Samsung's end today. I've tried so many things (assigning a reserved IP, changing DNS, hard reset on router, factory reset on tv, wired vs wireless connections, changing gateway, shutting down all my other connected devices on the network to give the tv some room, etc). When I talked to Samsung support, they told me they were experiencing an unusually high volume of calls. And at the end of it all, tech said that they were forwarding the problem to someone to work on... but wouldn't be contacting me back, to try again in a few hours. Which implies to me that there really is some sort of Samsung server that has to be pinged or cooperated with or whatever for your tv to be able to access your own network.
Long story short? I think we just have to wait it out...