Left my computer on with PreForm up, and went out.
Came back to PreForm NOT frozen (i can still do viewport operations - rotate the view, click-select the objects, move and rotate the objects, slice through the layers etc.) BUT all the menu items greyed out (except, for some reason, Customer Support and Go To Dashboard), as well as all the buttons, and all the controls in the status bar.
Hotkeys unresponsive as well.
Couldn’t quit it either, had to kill it via the Task manager.
Version 2.15.1, Windows 10.