Both version 2.1 and now 2.2 of ProRender have this issue, where while in viewport render if I interact with any objects, such as selecting them, the whole 3d viewport becomes large black squares. Sometimes it's almost all of it, and other times it is less, but it always does it EVERY single time. I included a picture of it. It does it when clicking on an already completed VP render, and immediately turns this way, and I have to zoom or orbit to get it to render again and clear up. It's not the biggest problem, but it is annoying.
This happens as soon as I click on any object to select it.............strange.