I have a dual screen set-up. I'm running windows 8.1. I have had this issue with Management studio 2008 R2, 2012 and 2014.
If I drag the management studio screen across to my 2nd display, and then close it down, when I open it again, it opens on the 2nd display. This is what I would expect. Unfortunately, the connect to server dialogue box is hidden from view and the main screen remains out of focus. It remains unresposive, waiting for the dialog that can't be found. I have tried ctrl-alt-tab and ctrl-alt-esc to find it but to no avail.
The only way I can sort it is to kill off the process. switch to single screen and then open it.
Does anyone know of a fix for this behaviour. Its really frustrating.