how about this also:
ping www.nfl.com and write the ip address (thank you nfl.com!)
reproduce the error and when you get page not found, go to command prompt and see what you can see. can you ping www.nfl.com by ip address? if yes, can you ping it by name (www.nfl.com) if no, you got isp dns problem. who the heck knows what but only thing you could do about it on your end is try for tech support on modem. maybe there is newer firmware or something
if no route to host found then you have problem maybe on your end. try to ping the cable modem by it's lan address. if you can't ping it, that is the symptom to take to modem tech support. they will try to blame it on other stuff like cablign or hubs/switches you may have in your setup so i would reproduce my problem with the stuff hooked directly to my computer using known good cables best of all the ones that came with it.