The recent security update for the Xbox 360 is to stop gamers outside of the US from accessing the US Xbox live marketplace. Many gamers have been exploiting the flaw in the security in order to access game downloads or demos that are only available in the States. With the recent launch of the TV and movie digital download service, Microsoft obviously feel it's about time that they acted on the problem and since the update any person who opens an Xbox live account must have a matching address for their credit card and home billling address.
Major Nelson goes into more detail on his website:
"Although we will continue to work on providing content and rolling out the service in other markets, US Marketplace offers will be restricted to the US only. This means that the credit card associated with your account is required to match the billing address and country your account is set up in. Note that we are not banning any of these Xbox Live accounts, as they can continue to use pre-paid subscription cards and Microsoft Points cards.
We also realise that there may be a small number of international users that were impacted by this change that have a legitimate reason for why their billing location does not match their account location. We are working to deal with these exceptions on a case by case basis and are working on a solution for these consumers."
Source : www.majornelson.com/