Our Internet is otherwise working, but I'm attempting to diagnose an IPv6 problem, so I thought I'd start by logging into the modem, which I don't think I have done before. It appears to be an SMC model, and we are using only the static IP addresses.
So I plugged a Windows 8 system into the modem, and it was assigned the IP address 10.1.10.10. I brought up a browser (Chrome) and attempted to connect to 10.1.10.1. It just sits there, while a "netstat" shows a connection to 10.1.10.1:http. After a while it times out. Connections to other sites work fine.