Many thanks to Eric for helping me sort out the Curve Editor problem. It turns out that in that version of the software, using Large system fonts (120 dpi) causes the Curve Editor to behave incorrectly. Using Normal system fonts (96 dpi), the Curve Editor works correctly. I'm at work so can't test the new build 19 software, but Eric stated that it should be fixed in that version.
I must say that Eric was very prompt, courteous and helpful. NP should be very happy to have him.
Looking forward to the software getting tweeked, and it's so, so nice not to have to unplug the unit in order to uninstall/reinstall software.