Update: developer token will be required in report downloads starting 
February 7th, 2012.
Based on recent AdWords API forum posts, many of you are unaware that on January 17th we began requiring a developer token in all post v13 report downloads.  As a result, we are temporarily rolling back this change to give you additional time to update your applications and upgrade to the latest version of the client libraries.  If you have already made this change, no action is required on your part.  We will enforce this requirement starting 
February 7th, 2012.
Minimum client library versions with support for providing the developerToken header in reports are as follows:
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