I not only downloaded the complete version but also the current update and tried updating from the Avast menu and rebooted and Avast is still showing 4.5.523 in the “About Avast” screen under the item Avast version 4.5 home edition;
Built nov 2004 [4.5.523]

But now we’re up to four addresses that are getting stripped

Is it possible that the heuristic settings could be causing this? I have them currently set to high, I shall try them in medium.

This kind of reminds me of what an intermittent electrical connection in automobile wiring is like when trying to find it.