The same problem as always: Lightroom's poor performance.
After several minutes of creating and editing Smart Collections Lightroom becomes very slow, simply clicking on one of them and waiting for the results takes 8-10 seconds.
I despair and double-click on a Smart Collection to edit it, but it doesn't respond. I double-click again several times and it does nothing. Finally presents me the editing window, but duplicated many times!
The only solution: close and open Lightroom. (And I was laughing at Microsoft applications)
Imac 27", 24 GB RAM
There seems to be only one window, but there are several perfectly aligned, so I spread them to show the mess: