I had exactly same problem, but I am new in Cubase, and lived with that couple of months, as I am not using Cubase much. Removing Cubase from NVidia driver helped me resolve this problem, I wrote in another topic (maybe it help):
I had exactly same problem, but I am new in Cubase, and lived with that couple of months, as I am not using Cubase much. Removing Cubase from NVidia driver helped me resolve this problem, I wrote in another topic (maybe it help):