I will add my experiences here. I have a CinchV2 project that I built with VS2010. When I use VS2012 (staying with .net 4.0 for the project) I also have these same issues with any of the behaviors and triggers, event to command etc..
What I find is that if I open the XAML, I see the errors you refer to in the error window and the intellisense errors in the XAML code. But close the xaml files and rebuild all and the program seems to run and behave as intended.
So, I'll show my ignorance here but is it possible that there is some disconnect between the assemblies Visual studio uses to compile the xaml for the designer and that which the application uses at runtime?
Also, if I build under VS2010 and then open the project under VS2012, the intellisense/XAML seems happy until I clean the solution. If I don't open the XAML files or Designer, I seem to be able to build, edit and run happily without any errors in the
Does any of this seem like what you're seeing?
I'd also *really* love to understand why this is and what I can do about it.