Thank you very much for choosing RadControls for Windows Phone and for your kind words.
In fact you should add the supported cultures at an application level and then everything should work just fine. I have verified this with a sample project. Could you please verify it at your side? If you are continuing to experience a problem I would kindly ask you to prepare a simple app that demonstrates the issue and open a new support ticket with the app attached so that I can have a closer look.
I am looking forward to your reply.
the Telerik team
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