I have a modded xbox using x3 chip. Everything is working great. I decicde to try xbox live out the other day and noticed that my xbox will not communicate with xbox live at all. I have not signed up for xbox live at this point but when I boot the M$Dash you go thru the configuration and it will test your cable, ip address, and dns then try to communicate to xbox live. Everything passes with flying colors except the communication with xbox live. I have another xbox that is modded so I tried it. This one does communicate with xbox live. When I test the connection status on this xbox it test the cable, ip address, dns and xbox live and they all pass. One of the differences I noticed between the 2 xboxes is the one that works, in the connection status screen at the top has a s/n:xxxxxxxx. The one that doesn't work has no s/n:. It is blank. Is this the cause of the problem and what is this s/n:? I know there is not a cable problem or network connectivity problem. I did find that my dsl router was blocking certain type of packets that xbox live requires but I called the manufacturer and they sent me a new firmware upgrade to fix that problem. I tried a new xbox that is not modded and it communicates ok as well. Anybody have any clues????