Thank you. That was it.
The update messed up the my Layout Presets. You can middle-mouse click to apply grades in 'All', and 'Color', but not when set to 'Sizing', which it had defaulted to.
Annoyingly, I can save my Layout Presets with Keyframe Timeline Mode set to 'Color', and it remembers that. But then sometimes it doesn't
In general I find Layout Presets pretty unstable using multiple monitors.