It is noteworthy that if you are using the AppBuilder browser-client (formerly known as Mist) there will be CORS issues when testing the behaviour of your app in the simulator. We'd recommend that you use the Windows or Visual Studio AppBuilder client.
Regards,
Steve
Telerik
Icenium is now Telerik AppBuilder, and is part of the Telerik Platform. For more information on the new name, and to learn more about the Platform, register for the free online keynote and webinar on Wednesday, February 12, 2014 at 11:00 a.m. ET (8:00 a.m. PT)