I haven't encountered any errors. Everything appears just fine when the console starts and when I start a game, I see a message across the bottom of the screen letting me know that I've been disconnected from Live. When I attempt to connect to Live, from within the game, I receive a simple message letting me know that it's not accessible. When I perform the test, it of course it closes the game out, logs me out and then the test runs fine without a problem.
It just so happens that I have another Xbox 260 console in the house and on the same network. I tried it and it worked just fine, I was able to play a game on the network. So, it doesn’t seem likely that there’s an issue with the network because it worked just fine until Monday and the other console on the same network has never had a problem. Below are the answers to the questions that you sought:
What Country/State/Province do you live in?
Modem brand & model number:
Motorola Surfboard MODEM
Router brand & model number:
Asus WL-500gPv2, sitting behind a Netgear WG5614v10
If Wireless, are you using a white or black external adapter, or an internal (Xbox 360S) adapter?
Not using wireless.
Things you have tried:
Cleaned off all cached game information from console along with profiles.
Is UPnP Enabled? Yes/no/Unknown
Do you have a NAT error? If so, what is your NAT?
No NAT errors encountered.
Any Error Codes you encounter:
Who is your ISP(Internet Service Provider)?
After you run "Test Xbox LIVE connection" press “Y” for "More Info”. In the pop-up that appears, what are the following values, if shown? (If a value below does not appear for you, just leave it blank.)