I'm going to make a wild guess that you're having a connection issue to the live service. Could you try powering off your modem/router for a couple of minutes, power the modem/router on again and then try clearing the cache etc again. If that does nothing
you could try resetting the network settings on the console.
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Turn off your console.
Wireless connection only: Unplug the Xbox 360 Wireless Networking Adapter from the USB port.
Turn on your console.
Go to My Xbox, and then select System Settings.
Select Network Settings.
Select Wired Network or the name of your wireless network, if you are prompted to do so.
Select Configure Network.
On the Additional Settings tab, select Restore to Factory Defaults.
Note This will only reset the network settings. This will not affect any other console settings.
Turn off your console.
Wireless connection only: Plug the Xbox 360 Wireless Networking Adapter back into the USB port (if you are using an adapter).
Turn on your console.
Wireless only: You will receive a message to configure wireless settings. Follow the on-screen instructions to connect to your wireless network.
Test your Xbox LIVE connection. To do this, go to My Xbox, select System Settings, select Network Settings, select Wired Network or your wireless network name (if you are prompted to do so), and then select Test Xbox LIVE Connection.