i seem to have solved this - I'd already tried control panel - internet options - security - set everything to default
. that had not worked so I went thru all the internet zone settings.
there is one called "launching applications and unsafe files"
- choices were enable, disable, prompt and it had defaulted to disable
. I changed it to "prompt"
& google now happily downloads calibre installer. strangely I don't get any "prompt" & windows does not do its annoying " blocked because this file came from another computer" trick either.
I'm still convinced that either a recent windows update or a chrome update messed with that setiing while I was not looking
( IIRC microsft rushas aout a browser security fix lat week - maybe they tweaked some default otpions )