Well, after changing the SSL settings as advised earlier, all the amber alerts disappeared.
However, when checking my email the following morning, I got a series of red alerts which said something along the lines that mail couldn't be collected because the servers needed SSL security - sorry, I was so hacked off that i didn't record the actual words.
Accordingly, I checked the SSL box for each mail account and downloaded my emails - but got the series of amber alerts yet again.
So, wanting neither a series of amber alerts or red alerts, which seem the only options, i've uninstalled avast! and will wait for a new version which hasn't tried too hard to be clever.
I'm not a geek, so I want a solution which will install and operate without any technical input (such as changing SSL settings when I don't have much real idea of what they are or what the implications may be) from me - like Sophos, clamXav or iAntivirus, all of which instal with little or no fuss.
Sorry avast!, this update seems a retrograde step to me.