We are making major updates to the v2009 Sandbox environment starting today and continuing throughout the week. Because of these changes, the v200902 Sandbox environment will be unavailable. We will post more information about what's new in the v2009 Sandbox environment once the work is complete--please stay tuned, and apologies for the downtime.
The v13 Sandbox environment should remain functional throughout this process.
-The AdWords API Team