I'm seeing a weird issue with the bottom border of the RibbonWindow being clipped or overlapped to about half the height it should be, but only when compiled under VS2012 (running under Win7). It's an easy repro - create a new project in VS2012, add a new window using the "Ribbon Window (WPF)" template, and change the App.xaml StartupUri to RibbonWindow1.xaml, then build and run the project. The bottom border of the window should be clipped. Now do exactly the same thing under VS2010, and everything appears as it should be. If you change the base class of RibbonWindow1 to a regular Window, everything appears as it should, except you lose all of the glass ribbon title functionality.
Let me know if you need additional info and/or screenshots - thanks.