Just to close the loop on this. After trashing my preferences (all of the adobe .plist files in both my library and the root library, the black frame problem went away for four days. This morning, I had one pop up again, so I again trashed my preferences and it hasn’t happened since then. So for the time being, I’m going to make it a habit of trashing my preferences every morning and we’ll see if that keeps the black frames away.