XNA Game Studio Express
What are the steps you take on the console before you get this error, and where does the error get displayed Are just having trouble getting connected to Live, or does this error only occur when you launch the XNA Game Launcher
--Stephen
This is actually a pretty simple networking issue. Every device on an IP network has to have an IP address. DHCP is the most common method of assigning IP addresses automatically. However, only ONE device on a network is allowed to be a DHCP server and assign these addresses, so a PC will typically not run one.
When you plug the xbox to your cable modem, the cable co is running a DHCP server, your XBox gets it's IP address, and goes on and is happy. When you plug the XBox directly to the PC, neither one is running a DHCP server, so...no IP address.
You can assign IP addresses manually on the 360, I think. Of course, getting all the numbers right if your networking experience is limited is not easy. You can't just bang things in and expect it to work.
Your best bet is probably to get one of the teeny 'connection sharing' routers that you can get an electronics shop for less than the price of a decent 360 game. You plug it into your cable modem, your PC, and your 360, everyone gets on the net at the same time, and the DHCP issue is solved. Most of those $50-$60 jobs are pretty easy to set up, often having a default configuration that is suitable for immediate use.