'sudden' wired router/modem/pc problem?

I have a sitecom wired router, and 2 home pcs. A motorola surfboard modem is connected to the router, plus to one of the pcs via usb cable. The router connects to both pcs via rj45 cables.

Everything woeked fine, getting internet access on both pcs, until yesterday. Now one pc has no inteernet (it doesn't list the motorola surfboard as an adaptor) and the other pc still has internet, but is not using the motorola surfboard, but its internal modem (I assume). The network connection for the motorola modem has weird ip addresses, not the 192.168.0.1 as before, but 169.254.214.152. I've tried to investigate as much as I can, and even disabled the pc's internal modem, but the motorola connection, though enabled, won't give internet access. I tried ipconfig/renew in command prompt, but it says the adapter is not in a permissable state..... please help, in plain english!!