Avast cut randomly connection

Good morning!

I think that Avast! Free Antivirus is cutting randomly my internet connection.

I was working with Mozilla Firefox and I think that heavy pages cut my PC connection. Also, hard disk is feeling like working to seek something. About 3-5 minutes, I can’t access Internet with web browsers, but any other programs using another port than 80 and 443 works fine.

I have also make full scan but any malware found. So, I’ve tried with Google Chrome. First day, it was working fine so I thought that it was about Mozilla Firefox. But the next day, the problem comes again.

Also, the problem happens more time when I’m using restricted connection (only a few websites are allowed, using squid).

And when the problem occurs, Avast UI is freezing. So, it is Avast! or something else ? How to solve it ?