Can only see selection if i hold down Ctrl - trying to cut out image

[Riverboat2001]

I'm editing a photo of my vehicle. I want to cut it out from the background and save it as a png to use as a logo.
But I'm failing at the first step.
Take image into edit mode.
create duplicate
Disable original image
create mask (on duplicate layer)
Select magic brush
and start painting.

But I can only see the marching ants if i hold down the control key.
What have i done to cause this, and how do i reset it so that i see the mask i'm creating.