Yeah I dont have a problem being banned for having a flashed FW, however when you see people playing online with the same FW as you, you have to asume that it cant be the firmware. Plus i got "Disconnected" before the server downtime, and was off for 7 days before buying a new console.
I read an old topic on xbox.com's forum ( search for "live failed" ), that there was a fault with refurbished consoles, i count find a definative answer or solutions as the thread was old and the links for the full thread were dead, it mentions cache clearing etc etc.
None of which got me back online, i contacted customer support who told me my account was fine and there was no problems at all at there end, they asked me to check my ports and such, went through the usual 15 minute script before the guys brain actually kicked in and his mouth began to work for itself.
I then asumed it must be an ISP fault, but a friend of mine that lives nearby was connecting fine.
So i took a gamble and bought a new console, and it worked first time, i then flashed the firmware with the latest hitachi FW and played online fine for the past 2 hours or so, i even managed to buy Lumines.
Tried my original 360 just now again and it is still failing the live test, and i wont be lossing on this 360, where i live there are many folk with no dsl/cable who will quite happily buy a pre modded console.