I have to think you're right. I think this is a multiple monitor problem. I'm running 4 monitors (3 using DVI and one LED TV attached via HDMI) but this was never an issuer with Logic 9. In L9 all my screen sets stayed put and worked flawlessly. Only when I switched to LPX did this start happening.
With the ability to pop open and closed all the different editors right in the main window, it seems to me that each new version of logic is moving more and more toward single monitor and/or laptop users. While I love the convenience of this, there are many professional film composers like myself, who use very large templates with multiple screen sets to speed our demanding and often eclectic workflow. I realize we're a small minority of users, and most are probably using Logic to create songs with no more than 30 or 40 tracks, but it would be great if Apple would keep us (professional power users) in mind as they continue to develop Logic Pro.
I hope we can gain some traction on this issue. I have posted it on the apple forums, which I understand the apple folks read. Those of you who are experiencing this problem - If you would, please take a sec and add to my post over there so the apple folks will know it's not a isolated issue and needs to be addressed. Here's a link. Thank you.
https://discussions.apple.com/message/23287708#23287708