Moving from WPF 3.5 to 4.0 causes error "Can't put a page in a Style"

Question

Hi,

I'm in the process of moving my application from .NET 3.5 to .NET 4.0, and I get the following error message : "Can't put a page in a Style". I've implemented the MVVM pattern for this application and use Data Templates to tell the application how to render my various view models...for example below.

<DataTemplate DataType="{x:Type vm:ConfigureAxViewModel}">
    <vw:ConfigureAxPage />
</DataTemplate>

Is there any way around this error? Do I have to make my pages controls?

Thanks, Roy