Xbox 360 Hardware Question
What kind of router do you have?
hmmwell you have to go to your router settings and keep UPnP open and here is a helpful site www.noddegamra.co.uk/problems-with-xbox-360-live-nat-settings/3/
What brand and model of router do you have?
HMM i think you should try to port forward www.portforward.com/ this site helped quite a bit it is basically a walk through process
Walkthroughs & FAQs
Xbox 360 Hardware Navigation