My first problem is that I cannot connect to Xbox live through my Comcast cable modem. The automatic settings are not working on the Xbox to provide a connection. I have tried turning off the modem to reset. Turning off the Xbox to reset as well as manually setting the Xbox configuration.
It's possible that your router isn't configured to allow network traffic across the ports in order for it to make a connection with the xbox live servers.
box LIVE requires the following ports to be open:
You need to have port forwarding setup between the modem/router for the following ports.
* TCP 80
* UDP 88
* UDP 3074
* TCP 3074
* UDP 53
* TCP 53
Another way to do it is to activate Universal Plug and Play if your modem/router supports that. It can be a security risk. But it basically lets your Xbox request for the ports it needs in order to access the Xbox live servers.