It happens like this. First i wait that picture is rendered…then i push “File” then rendering starts…It is very annoying.
Why does it happen.
I’ve also noticed this sometimes. It happens because Blender still “thinks” you are clicking the Render button even when you click elsewhere. Now whenever a render finishes for me, I click on the Blender thing on the Taskbar (in Windows) and then go to the File menu. Doesn’t re-render.
Or maybe just use F3 
I’ve had a bizzare bug where when ive rendered an image, an i click to close the window, blender thinks im clicking in the main program window, usually where the mouse pointer was located the last time the main screen was active. very weird.
robdollar: Well, in fact you aren’t supposed to use your window manager’s widgets at all to handle Blender Windows, but exclusively use Blender’s functionality for handling them.