Thanks again, Grim, for helping out. You are correct that upon first startup after updating to v 10, Cubase actually did blacklist the Waveshell VST3, so I made an exception for it in the Plugin Manager. After that I got the scanning hangs on starting Cubase.
Waves support sugvested uninstalling and then reinstalling my Waves stuff. I did so, but the problem still persists. I am now waiting for Waves support to remotely access my computer and set things straight again.
Words cannot adequately describe my frustration at a simple update causing me all this headache. It is 2018, not 1999, and I very strongly feel that version updates should be a straightforward matter.
/Magnus