I had similar problems with Comcast cable. I used to be able to log onto Xbox Live through a USB hub (not a router) while the computer was online with no problems. Then mysteriously Xbox Live wouldn't work.
Without telling anyone, Comcast began to limit all customers to a single IP (unless you pay extra). To get Xbox Live to work, I had to connect the modem to the Xbox only and reboot it to get a new IP. I've since moved to a router, which works great.
Bookmarks