Have you tried cycling both the computer and modem? Turn everything off and unplug. Then power your modem, and when all but the top light are lit ( or it may light), power the computer on. I'm assuming the computer is connected directly to the modem. If there is a router being used, modem first, then router, then computer. Wait until each is fully on before powering on the next. This sometimes helps when I have the same glitch.