Following the advice, I looked through what I had installed since a known successful period, and the ZoneAlarm fell into that category.
In addition to uninstalling ZA I uninstalled Java (again) and several other 'unwanted' items (such as the bitching messages for an initially free programme that was supplied installed with the computer now requesting payment).
I then followed the link for Java and installed it and, hey presto! it worked . . .
The only 'annoyance' was the constant restarts required between uninstalls.