There is a new version of the Windows Azure platform AppFabric SDK was made available yesterday, you can get it here . There was also a scheduled outage of the service yesterday while the team did a “major software upgrade”, presumably this is tidying things up in advance of going production live on Jan 1. There was a pre-announcement of breaking changes posted here , but… I missed that. My first clue that something had changed was that the Access Control Service wasn’t talking to me anymore :)....