New GUI and Stuck UnsupportedClassVersionError

Hi,
I think I followed the steps in the online docs for generating form using the designer. When I preview I get this runtime exception:

UnsupportedClassVersionError: com/intellij/uiDesigner/core/GridLayoutManager

Also, can someone how I create a new class that is bound to the GUI form?

quick overview:

I have a class that extends JFrame it has a constructor than looks like this:

MainWindow(String title, GraphicsConfiguration gc, JPanel searchPanel);

In some other code, I imagine in need to create a MainWindow object - but where do I get the GraphicsConfiguration from?

If there is any other docs for the UI Builder available, I'd appreciate the pointer.

Thanks much, Spencer