forms wont open in design view

Question

Hi guys,

I'm workin on a project containing many classes and forms.

When i try to open some of the forms in design view they display an error like this: http://www.buncrana.com/uploads/VS-Design-Error.JPG (click for screenshot).

The application compiles and executes as expected.

Here is a simple class diagram: http://www.buncrana.com/uploads/UML-VS-DesignView.JPG

PropertyPage inherits UserControl, PropertyPage does very little and does nothing to effect the appearance of the window.

DateTimePropertysPage extends PropertyPage and has an "InitializeComponent()" method.  

Any sugegstions?
Thanks in advance,

David