'Binding' type does not have a matching DependencyObjectType error

This is one of those blog posts so that I can easily remember what causes this particular problem.  In the Virtual Tour Viewer, I have found on occasions with .net 4.0 that if you press the back button, to go back to a previous page you get a “'Binding' type does not have a matching DependencyObjectType” exception.

As it turns out this is because I had PresentationTraceSources in the page. e.g:

OlsImage="{Binding SmallImageFile,PresentationTraceSources.TraceLevel=High}"

If you remove the reference to PresentationTraceSources  (which allows you to debug bindings), then the problem goes away!

interestingly, this exception only occurs when using the back button – if I go directly to a page there is no problem.  Weird, eh?