If you run Windows with multiple screens enabled, one of them is known as the primary screen and Windows (by default, i.e. without thrid party tools) displays the task bar and the start button on that display.
If you move any of your Notes windows to a secondary screen and then click a pop-up menu from the status bar (e.g. the location selector), the pop-up will actually appear on the primary screen (where you may not even have a Notes window). Depending on the ratio of screen resolutions between you r two screens, it may also be positioned outside of the displayable area.

I guess the correct behavior is pretty obvious, pop-ups should appear on the screen where the UI control is located already and the property box should at least be movabl e to any screen.
A related issue happens with the property box, this will always open on the primary screen as well and can't be moved to the secondary screen (at least not entirely, the movement stops when the property box is half off the primary screen).