How to resolve VS2010 Windows Form Designer issue (base class could not be loaded)

Question

I have recently been getting an error in the Windows Forms designer of VS2010SP1 when using inherited UserControls.

The error is

The designer

Answer 1

1. Clean Project (not sure if this is necessary)
2. Set build to Release
3. Rebuild Project

The forms designer will not rebuild the forms that you manually edited if you build the project in Debug mode apparently.