I Went through the same problems and i figured out that the only thing not allowing me to connect to my Xbox was a firewall issue. When going to the admin page for Comcast. Address 10.0.0.1. I change my firewall settings to medium and saved it and now my Xbox works great. I'm not to sure what part of the maximum firewall protection stopped it from connecting to my Xbox but now that it is changed to medium there are no more issues.