Is it an Arris, from ATT? My iPhone sometimes can't log in and it shows that the password entered is incorrect, even though I know it well (from the need to re-enter it so damn often). I had set up a guest network with a different SSID and password, but disabled it a long time ago. Most of the time, I can connect if I use the password for the guest network. ATT is no help at all, they don't offer a stand-alone modem for U-Verse, so I just live with it.