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Avast Free Antivirus / Premium Security
1

there nothing to do and perhaps Avast will correct it on newer releases,But for the time being I have found a solution,
just install an old version 11.2.2261 (i use this) and do not update program,just update virus definition,ii works.I am sticking to Avast,it`s for sure.

2

Have you tried this ???

Repair Avast:
Control Panel> Program and Features (Add/remove program)>Select Avast> Select Repair. Reboot when completed
https://www.avast.com/faq.php?article=AVKB204

If Repair doesn’t fix the problem, try the following:
Clean Install of Avast:
https://goo.gl/4Ptzkf
If you need additional help with the Clean Install, watch this:
https://youtu.be/p-h3myRD51A