Sorry for the panic, all seems well now.
I just reinstalled it a third time, new release v.1.9 is now working.
The auto-updater downloaded the new version as I was using Firebug to do
some webwork. Firebug just stopped working all of a sudden. I restarted
Firefox but Firebug still did not work. I uninstalled Firebug and then
reinstalled it, twice. Then I uninstalled it again and installed v.1.8 last
release, that worked. Then I uninstalled v.1.8, reinstalled v.1.9 and it is
DOA is 'dead on arrival' :)