Same problem again. Been going on a week now. Modem is working, all lights on, stats look good. But I have no connection. Windows can not connect to the DNS server. No it's not Windows, I have a mini mac on the same service and it will not connect either. Called but they can't find anything wrong. They want to send out a tech, but there is nothing wrong here. I've been a customer for 8 years and have been satisfied with this service, but if this is not fixed soon I will cancel and find something else.
Did your configuration lose the DNS server address maybe? Go to a command prompt and run ipconfig /all and look at DNS addresses. There should be 2 of them. Try to ping google.com. Try to ping 188.8.131.52. If ping by IP works but ping by name doesn't you have DNS servr issue. If blank go to network properties for the pc and tell it to not use autimatic and enter googles DNS address. .... 184.108.40.206 and 220.127.116.11.
Go to your modem status page - on the bottom, determine if the Web Acceleration is connected or not. Recently, I've experience it being more frequently disconnected than in the past and typically has been an outage at my core node. When disconnected nothing works despite all green idiot lights.
It stayed off for about 3 hours and then starting working. This only happens in the mornings when I first turn everything on. Sometimes it's only off for 20 or 30 minutes, sometimes for hours. Web acceleration is disconnected when it's not working. If it does it again in the morning I will try the DNS solution posted by Harvey.
Problem continues again today. This time in the middle of the day. Was down a couple of hours. All looks fine, even windows shows I have a internet connection, but can not resolve a webpage. Web acceleration shows disconnected in the modem stats. Changing the DNS servers addresses does not help.