I don't know if this is much use too anyone, it might be for those with a modded xbox using ICS as there connection. I searched for various words and didn't find anything, so i assume, noone, as of yet, has looked at it.
I was trying too get on xbox live the other night (I'm on 56k, and was bored) and hooked everything up, setup IPs and so forth through the dash. And clicked connect, it failed, i knew nothing was wrong with settings or the cable, so i thought it might of been a firewall issue. (which i had had before when trying too use Apache, FTP Servers, etc). So i went through the process of allowing certain windows processes access too the internet, one by one.
I came across Generic Host Process for Win32 Services
run by svchost.exe, which most people should know, is a dummy type program. Anyway, that fixed it, i connected and boom live update, so i blocked it and the connection failed. I decided too block it and connect too UnleashX FTP, and it worked.
So just a recap, if you grab a firewall and block that service, you can block xbox live and still keep ftp abilities, obviously LinksX and Skin Downloads and such won't work either, hope someone finds this handy dandy. Since it's easier then flicking switches, removing cables, etc.
Even better would be if someone wrote a program that JUST blocked that program and could just toggle it on and off, which you can still do in the firewall, but hey, it'd look spiffy