go to your computer and log in then go to the start button, there is something that says "Run..." click on it, type cmd in that box, a black screen should come up type in ipconfig/all then find where it says physical address, write it down on a piece of paper. Now, if there is any games in ur xbox take them out and turn on, go to system, then go to network settings, then goto edit settings and go to additional settings and go down to where it says alterinate mac adress then as an alterinate mac address type in the thing you wrote down on the paper. Try to connect to live again now. i had the same problem at first mat and i done this.