Thank you, Kenny, Dennis & Alan -- and especially to Alan, who gave the key clue
Problem now solved, after little effort...
Just to let you all know what worked and what didn't...
1 -- Tried IE and got a message that said 'your current security settings do not allow this file can be downloaded'
2 -- Tried launching Firefox in safe mode -- This resulted in another 'empty download'
3 -- Went into IE; set the security settings to Low, then back to Firefox (as a test), and was able to successfully download the CCleaner file...
Then went back to IE, reset the security settings to where they had been (Medium-High),
and set about to continue on with 'life as we know it'...
Was also able at this point to download the zip-file version of CCleaner, so I take that as a good tip for the future...
Again, many thanks to you all...
Much appreciated...
SJB