In accordance with our policy of sunsetting older versions of the AdWords API, we will turn off access to version 11 of the API on Tuesday, August 26, 2008. Version 12 of the API has been available for over four months now, and supports a number of new features. We hope that you've already taken the opportunity to upgrade your code.
The latest versions of the publicly available client libraries all support version 12 of the API, so if you're using one of those, please check the relevant README file for information on how to switch from version 11 to 12. The migration process should be fairly straightforward, but one thing in particular to watch out for is that ad group ids are no longer ints; they're now longs in version 12.
As always, if you have any questions about the AdWords API or upgrading to our latest versions, you can check out our Frequently Asked Questions or ask them in our developer forum.
-Jeffrey Posnick, AdWords API Team