Cloussau,
I do not want to fault you but there is, it seems to me, some logic lacking in your suggestion.
When these users installed the new release of avast, they, as I did, had to update the program permissions for all the changed avast components in ZoneAlarm. Frankly , I am beginning to think this old story blaming things on forgotten permissions in ZoneAlarm is an urban myth. It is not something I have ever seen in my use of that product.
Anyway, if it is ZoneAlarm at fault, why on earth does not ZoneAlarm cause exactly the same problem when they reinstall 691, as many have done and find the avast update problem has disappeared.
I have yet to see one report in this forum of someone experiencing this problem, who then chose to revert to using 691 and then continued to experience any difficulty.
I hope that the avast team is working more closely with someone experiencing this error than we are seeing reported here.
I am sure that most of the user base have updated without problems, but there certainly seem to be quite a few users reporting the same issue in several threads who must be feeling rather frustrated.
Perhaps the avast team can provide a status update on their current take on this problem.