your summary is correct.
I tried the steps you suggested and got some new info:
Loading different basemap; same behavior.
Reboot machine; no change.
Create new mxd with same data; at first it worked properly, all features
visible. The features were no longer visible when I applied rotation to
the data frame. As long as I set the rotation to zero, I can see my
features. When I set the rotation to a different value, they are
obscured. I experimented with several values, my preferred setting for
this map is 118 deg., only zero worked.
Charlie