For those Google AdWords API developers, you should be aware that currently any requests sent over the SOAP protocol to the API Sandbox will return an error.

A Google Groups thread has one developer complaining and an official Google representative confirming the issue. Jeff Posnick from the AdWords API Team said:

Typically, sandbox errors are not fixed as quickly as production errors. But since the API is returning errors for all SOAP requests, I have a feeling this will be fixed faster than an normal sandbox bug.

Forum discussion at Google Groups.