I don't know how it happened, but when I use any of the trackballs in Bryce3, a box appears as in the image attached. Just started happening. What's this all about?

It sounds like you accidentally turned on the Nano Editor. This is one of those hidden icons on the righthand side of the Bryce screen that only show up when you move your mouse over them. Slide your mouse over to the right, go up through the little icons until you see "Nano Editor On/Off" displayed under the trackball. Click on the icon. That should restore things.

Thanks. That was it.

LOLOL--learn something new every day. I never bothered with that before and I guess at some point I must have read about it in the manual, but sure didn't remember it. Glad it came up. Diane B