VS 2010 Lost my form.

Hi. I am new to Visual Basic, although I have many years of experience with PICK basic. This is my first VB project.

When I open my project, I no longer see the form (there is only one) in the editor. The file named FormCatsyl.vb appears in the Solution Explorer, but when I click on it I get the following error message: "There is no editor available for 'C:\....\FormCatsyl.vb'. Make sure the application for the file type (.vb) is installed."

I'm not sure what I did wrong. I've worked around it by creating a new project with a new form, but I would like to avoid this error in the future.

Thanks.
Dave