Hello,
I have seen this behaviour both before and after the update.
Menus would not open, submenus would not appear. A few times it would appear suddenly, following a flickering of the screen, but most often it followed after keeping Terragen open a long time and making many changes, alternating tabs etc. The most usual event that started it was when I tried a different seed in a population, checked the "preview" button, unchecked and tried again. After a few times of this, the GUI stopped responding.
Minimizing Terragen for a few minutes, sometimes restored the problem, but it was unsteady afterwards. Once I tried rendering after the function was restored and the rendering stopped as soon as it began. The window caption was: "Rendering (0:0:01s)" and the CPU usage was 0%.
Most often there was no memory or resource problem and if I started other programs, they worked as usual. But, there was a similar problem on the desktop, when Terragen was that way. Right clicking and double clicking did not work. Only the tray menu programs could start, which did not need double clicking. The desktop came to normal, as soon as Terragen closed or was closed by Task manager.
I thought it might be a problem with the visual something used to make the GUI - maybe I don't have the right version of the runtimes or it is corrupted.
Helen