Rob, I tried your suggestion of changing screen resolutions, for several values down to 800x600, but the toolboxes would not appear. Then I tried editing dc_draw.ini and that would change the default line style. That might have solved my problem even without the toolboxes except that one drawing that I have been working on ignores the .ini setting and insists on using the line style to which it had spontaneously changed. This unwanted change has happened before, always to the same line style (continuous), but in the past I was able to change it back with the line style toolbox.
I looked at the registry, following your path, and two of the command bars (5 and 9) had really outlandish numbers for xpos. Like 4294936576 decimal, whereas non of the others are greater than 5000, and most a few hundred. If I change them, does the effect require a reboot?