Thanks for writing.
I am afraid that RadHubTile and its derivatives are not made for serialization. I suggest reorganizing your app, so that the hub tiles use data binding to display information contained in view models. This way you have full control over the data and its serialization (the view models) and the hub tiles will be left as the visualization components that they are.
Also, in order to save images to isolated storage you have to conver them to int arrays. You can do this with the help of writeable bitmap for example.
the Telerik team
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