Dear LR Forums,
I've been experiencing this for quite some time on several different MacBooks so I figured I'd ask to see if it is a known issue and if there is a workaround for it.
I use my MBP daily between my desk environment, where I use a 2nd monitor, and just as a standalone laptop.
Frequently, when switching back and forth, I will go into LR and attempt to work, but certain parts of the screen won't respond to mouse clicks or mouse-over.
I've figured out that if I do a 'Fn+F11', it will bring up the 2nd monitor preview window, and then I can click 'Fn+F11' again and the window and the issue will go away, until I switch Desktops (Ctrl+<RightArrow> or Ctrl+<LeftArrow>) at which time the issue returns. If I close and restart LR, the issue goes away again until I plug in the 2nd monitor and enable the 2nd monitor preview.
While the 2nd monitor is active, the issue does not exist, its just after the 2nd monitor is removed that the problem happens.
I had hoped this was a known issue and was addressed in a future release, but, I've been seeing this since LR4 or LR3 I believe.
Note: That command is 'Fn+Command+F11' not 'Fn+F11' as I posted above....
Am I the only one to ever experience this one? Wow, ok, time to open up a bug report.