Update: As of July 9th, 2015, this temporary limit has been removed.
To ensure reliable performance for all advertisers during 
advanced URL upgrades, the AdWords API has placed a temporary limit on the number of 
AdGroupAd ADD operations that can be performed on an advertiser account per day. Other types of requests are not affected by this change. Please review the 
RateLimit documentation and make sure your code handles the 
RateExceededError properly.
During most normal operations, you won’t run into these limits. However, if you are uploading a very large amount of new ads in a short period of time and find yourself running into this error frequently, let us know on 
our forum and we will work with you to address the issues.
 Anash P. Oommen, AdWords API Team
 Anash P. Oommen, AdWords API Team