How do I fix the IP address failure message when i test my x box 360 LIVE connection????

Im trying to connect to LIVE and when i test my connection it always says IP address failed, i have earthlink high speed dsl and i have an apple express router connected to that...i connect my 360 to my computer and under the router's settings i check the box that says share the connection...what can i do to fix this problem??????|||There are a few things that could be wrong. 1) you're not forwarding the required ports on your router. 2) you're blocking the mac address of the 360.|||You're using a router to connect to a computer that's doing internet connection sharing? That's 2 address translations. Three, if your modem is also a router. You have to get rid of 1 (or 2) address translations. How you do that depends on the make and model of modem and the make and model of router. (You connect the XBox to the router, not to the computer.)