I have recently upgraded to VS 2012, I had to as I needed to start using the .net 4.5 but that is besides the point. My problem is the following:
I have a Resource
you can create a common or infrastructure project from which other projects will reference. Add your resouce resources. Then create a pack URI. then reference in your usercontrol or window resources within a resource dictionary
<...Resources>
In the usercontrol or use Window.Resources in the case of a window. This works for me.