Everytime I turn on the XBOX it says "a system update is available from XBOX Live. If you decline you won't be able to connect to XBOX Live until you take the update". I press yes to update and it goes to update processing and immediately the system restarts. When I decline the update it says "some XBOX 360 features are missing or corrupt. A system update is required to replace them. Your console will now restart". Someone please help..I've tried using a USB update and the system does not even acknowledge the flash drive.