I tried a clean uninstall (including removal of Electrum folder) and a reinstall. Same issue.
I then looked through all open issues in Electrum GitHub, and found this:
"Silent crash on Windows7 if path to AppData\Roaming\Electrum contains national characters" (
https://github.com/spesmilo/electrum/issues/2376)
It appears the cause may be that my user name contains a national character, i.e. the Danish letter "æ" (a+e ligature).
Apparently this causes Electrum to crash silently. I made a comment on the issue - hopefully the bug will be fixed.
Meanwhile, I can run the portable version of Electrum, since this will allow me to start in any folder, not just my home folder.
Thanks for your help.