I use dual display workspace and invoking secondary display now by whichever means puts it on primary monitor as smaller floating window, as would happen if I was using a single display workspace. Enabling full screen display of secondary display maximises it to size of secondary monitor while retaining it on primary monitor (i.e. producing cropped secondary display on primary monitor). Resetting or deleting Preferences interestingly returns secondary display to appropriate size on correct monitor for the first usage but thereafter secondary display appears again on primary monitor as smaller floating window (when full screen secondary display is disabled). I upgraded to LR 6.10.1 but that made no difference. I then uninstalled LR with the Uninstaller then re-installed but the problem remained exactly the same. I use OS X El Capitan 10.11.6 in an early 2009 Mac Pro with 16 Gb RAM, a 120 GB SSD startup disc and ATI Radeon HD 4870 512 MB graphics card (but the hardware setup worked fine until recently so I don't think the problem is hardware). Secondary monitor is an Eizo ColorEdge CG243W. My guess is it's an OS X issue, but how to fix it?
