Last week, there were reports of the Google AdWords API not functioning properly. In particular, the "quota units used" counter was not changing, nor were usage counters retrieved via API.
When this was reported (7/21), Jeff Posnick (AdWords API Advisor) acknowledged that there was a database issue on Google's end and reported this to the engineering team.
Yesterday, Jeff updated us to say that the Google engineering team has fixed the problem. Missing data from July 17th and onwards was backfilled and Google believes the problem to be fully resolved at this time.
Forum discussion continues at Google Groups.