I am getting the following error when building my application:

The attachable property 'VisualStateGroups' was not found in type
'VisualStateManager'. This reference comes from a theme I am applying to
the application.

Although I am getting this error the application runs fine but I cannot view
any of my pages in the Designer and get this error:

Problem Loading

The document contains errors that must be fixed before the designer can be
loaded. Reload the designer after you have fixed the errors.

Then in the designer, there are no errors.

Anyone know of any fixes? Right now I am pretty disgusted with MS and
VS2008, cannot believe all of the problems I am having. I just started a
new project using VS2008 and WPF and have had nothing but problems. Either
I get the most generic errors and have to go through the entire application
to find them or the designer will not display properly or the entire
application just locks up.