I have to stress this to people... The point of the XTest is for people who can't log in, not for people who can't see a game in Halo or whatever...There's 1001 reasons why something like that wouldn't work. Some include: wrong wireless network setup, different region, not enough bandwidth etc etc...
Odinstorm - Don't use the wireless card on your laptop. You'll only be able to get XLink FULLY working if you get your XBox a WEB (Wireless Ethernet Bridge), or hardwire your laptop to the router. Plenty of people including myself have tried this. Search and you shall find...
MikeF - Looks like you shouldn't have any troubles logging in, although you haven't said so or not? The XTest appears fine.
SlipperyKING - The packets from the XServer aren't landing at your machine. Possibly a firewall? Check thoroughly and either disable any firewall you have running, or work out a way to let it bypass the ports XLink requires.
Warthog - You've got a fine XTest result, and I can tell because you're telling me you can log in successfully. What you're experiencing is more likely game compatibility / host issues. Try another game with another person and be more persistent. Halo does not = system link games. There are 29 others supported on XLink which have much less issues to deal with.
Dirkbox - Same thing as SlipperyKING.
AND COULD PEOPLE PLEASE POST MORE INFORMATION, NOT JUST 'HELP PLEASE'. NETWORK CONFIG, PORT-FORWARDS ETC ETC...