When I try to load the form into the Visual Studio 2010 designer, I get the error message that "Value cannot be null, Parameter name: objectType. This is a form that loaded without problems in the VS 2005 and VS 2008 versions. It is a form that serves as a base form to other forms in solution and oddly, the forms that inherit from this form load into the designer correctly without error (at least for now).
If I click on the "Ignore and Continue" link, then the designer does load the form. However, there are some Handles clauses that get removed from the event handlers of one of the controls on the form. I noticed that there are other posts that report a similar problem that results in Handles clauses being removed from code.
I tried adding the Handles clauses back, but the next time I try to being the form into the designer it reverts to having the "Value cannot be null...." problem.