Just a note, when PinballX is run in windowed mode it can run in a kind of single screen mode and move the backglass and dmd windows - so the position you see in the screenshot might not be the same positions that they are when you run PinballX full screen.
My guess is that either it's the startup dc2 messing things up as Mike suggests or your windows screen numbers have got fudged over time and don't match what PinballX thinks they are (on my setup even windows and nvidia disagree about the screen numbers).
So try disabling the dc2 startup script first to see if that fixes things.. if not then you could try changing the screen numbers for the backglass and dmd to 3,4 and 5 and see if you find a combination that works (an alternative to this would be to set the screen numbers to the same as your playfield monitor and then use the x and y offsets to set as an absolute position from the top left/right of the entire desktop).
Welcome back, and thanks - a lot of your posts helped me out a lot when i was starting out