WPF Animation "Cannot freeze this Storyboard timeline tree for use across threads"
Can you post your Storyboard? It sounds like you have some kind of Binding in the Storyboard definition.
Ok so, as I suspected, it's because you're using a Binding in your Storyboard. You can't do this because WPF attempts to freeze all the resources leveraged by a template for efficiency and when you use a Binding on a Freezable, in this case the Storyboard, it prevents it from being able to be frozen.
Old question but might be useful for other people.Sometimes creating the Storyboard in the code-behind can be simpler: https://stackoverflow.com/a/10848781/779521