Thanks for your response.
I've already clearly stated what it is I want to do.
But here it is again: I want to get a rectangular ( or square) shaped image with rounded corners.
I know that: "all you SHOULD need to do is invert the mask".
Obviously if I could do that I'd be happily on my way. A bother to no one.
I'm just getting a rounded solid rectangular shape.
I'm not getting a rectangular selection ( marching ants)
I've done it with other images as I stated before.
Maybe this forum is still a good place to find the solution.
It's worked before.
I thought I'd give it another shot.
You never know.
Like fishing.