I am using MAC OSX 10.9.4 and LR5 Ver 5.6. I can't drag LR to my second screen. It's always worked before. All of my other apps drag to the second screen with no issues. I've re-booted my computer…
Make sure you are not in one of the full screen modes. Window > Screen Mode > Normal Can you see the "Traffic Lights" at the top left of the Lightroom window?
