The Google AdWords API Help forum notifies us that the AdWords API is undergoing unscheduled maintenance since late last night.

This impacts users of v2009 of the AdWords API only.

Eric Koleda from the AdWords API Team team said:

Stan Grinberg from the AdWords API Team added that this is “only affecting v2009 of AdWords API.”

Currently, there has been no update on the status of this unscheduled maintenance.

So if you have issues with the API, you now know why.

Forum discussion at Google AdWords API Help.