I have a problem with my Fedora box and cable modem. I'm not sure if the problem is on my side, or ISP side (Shaw cable). Of course, ISP claims it is not them, what else would you expect ;-)
I don't have an answer - but back when I had a cable modem, everytime it would rain - I would lose service half an hour later - and wouldn't get it back until after it stopped raining ...