Form suddenly broken

[AlexanderBB]

Was designing a Form and everything working fine when all of a sudden everything you click on "dings" at you.

I have to Control-Beak and the code is hung on the Line MyForm.Show.

Pressing F8 re-runs the same subroutine and/or (at times) has brought up

Run-time error '400':
Form already displayed; can't show modally

From Google
You can't use the Show method to display a visible form as modal. This error has the following cause and solution:

You tried to use Show, with the style argument set to 1 - vbModal, on an already visible form.

Use either the Unload statement or the Hide method on the form before trying to show it as a modal form.

I do have ShowModal set true, but this has been ok for three days until now.

I've tried setting this False also put unload before show, but it makes no difference.
Can anyone help, please

 

[AlexanderBB]

I meant to say I'm remmed out all the code in the Form too.
For a test I exported the Form to a new instance of Excel and the problem remained.
So I made a new Form, copied everything from the original, and it tested ok.

I then deleted it from the original workbook, and imported the replacement and that works too.

Suppose that means the Form corrupted itself for no apparent reason. That's a bit of a worry...

It is a common occurrence? Are there better / other fixes or solutions?