This hotfix rollup fixes several issues in the WPF Designer. This hotfix rollup applies only to the computer that has Visual Studio 2008 Service Pack 1 installed.
•When a resource in an external resource dictionary is updated, Visual Studio 2008 crashes.
•WPF Designer cannot load read-only attached properties, such as the VisualStateManager.VisualStateGroups property.
•If users or codes set a data binding locally, and then the users or codes clear the data binding, WPF designer reports the following error message:
'System.Windows.Data.Binding' is not a valid value for property
•If a Win32 project is set as the startup project, WPF Designer cannot load solutions in Visual Studio 2008 or in Visual Studio 2008 Service Pack 1.
•When you set and then delete the Source property of a WPF WebBrowser control, Visual Studio crashes.
•When you move a control that uses the MultiTrigger class or the DataTrigger class in the Style class, WPF Designer may generate an InvalidCastException exception.
KB Link - http://support.microsoft.com/kb/958017