Hi, since a few weeks I occasionally encounter this problem - when I click on a picture suddenly all the four side frames go blank, full black. There is no way to restore them but by restarting LR.
I have the latest version of LR CC installed on a Mac running Sierra 10.12.2; never had this issue before.
You don't state what version NUMBER of Lightroom you are using, but if you are using Lightroom CC 2015.8, then this is a known bug and right know the only fix is to reinstall the previous version CC 2015.7.
dj thank you so much - it is annoying but I may wait until the next version comes out :-)