Via Avast Ticket: #MCN-504-92599 we found out that my problems with internet and downloads in Vista was a collision between Avast 10.3.2225 and HitmanPro Alert.
As far a I know this problem was not analized.
So we now do not know if this is a bug in Avast or HitmanPro Alert of both.
I got only this answer:
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We do not recommend you to use more than one security application on one computer. This can cause a lot of conflict.
You should uninstall HitmanPro.
Anyway, new program version has been released this week Avast 2015 R4 beta 1 (build number 2015.10.4.2227).
........
Miroslav Jenšík
Technical Support Engineer
AVAST Software s.r.o.
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So they do not even know the difference between HitmanPro and HitmanPro Alert
In this answer it is suggested to test the problem in my Vista system with 10.4.2227.
MartinZ,
In your list of changes I do not see anything that has to do with my problem in Vista.
Can you approve that in Avast 10.4.2227 something is changed in relation to my severe problem.