The panels in LR turn black regularly. When this happens I'm unable to continue working. The only solution to this problem is to minimise or restart LR.
This problem occurs in all modules.
Who can help me out?
This is a known problem, for which there is no solution in Lightroom 6.8 at this time.
One solution is to re-install Lightroom 6.7. https://www.lightroomqueen.com/roll-back-update-previous/
Thanks for the response: that seems to have solved it.