Hi.
Just installed latest avast premier version 17.3.2291 (build 17.3.3443.0) and right after that my firefox browser has become more slower. It loads web pages much longer time and I also get “The Connection to the server was reset” error messages. My firefox version is 52.0.2 and operating system is windows 8.1 with latest updates.
Anyone else has same problem? Thanks if you can help me with this issue 
This may not solve your issue, but can be tried.
Try turning off shield that affect internet connection. Firewall, Web Shield, Real Site etc.
See if your Firefox can load webpage faster. If not, make sure your Firefox is updated.
Seems pointless to run a real-time protection a/v if one is going to turn off all protection against infection and malware because of a slowdown in browser speed and connectivity. The recommended action will certainly speed up browser behavior, but at what potential cost?
Suggest going to the firewall settings in Premier, and turn off port scanning. Leave all other real-time scanners active. I’m sure you do not get the server reset notice on all sites, just some of them.
Known bug in this build .2991, will be fixed in the next release.
Sometimes a couple of Windows restarts after an Avast program update can help.
Hi again.
I turned port scan off and that helped. Hope they fix this problem in next version.
Thanks for help!
Please follow Gopher John’s advice and read the following from Asyn: https://forum.avast.com/index.php?topic=199857.msg1388211#msg1388211
Micro-update for port scanning issue is available.
If you don’t wish to wait 12 hours for microupdate to arrive, reboot, connect to the internet, wait 10 minutes, reboot again.