Thank you for taking the time to tell me of the solution that worked for you.
The instructions were rather intimidating but as far as I know, I followed them and all seemed to work correctly. Then I re-registered and loaded an existing tree. The tree all looked OK. Unfortunately it still does the same thing if I try to go back and change one of the search parameters - gray screen, no control, etc. So then I tried just entering a new test tree from scratch. Unfortunately, it too has the same search problem. I think I'll just put up with it for now.