Being as how it's a Clean install of OS we can rule out another 3RD Party Antivirus Software.
I'm not aware of any 'specific' issue with your OS and Avast.
Did you run a "Custom Install"?
I recall an issue I had some time ago and decided to track it down. I used the "Custom Install" option in the installer and only installed the essential SHIELDS and none of the components in the "Tools" column.
Seemed to work at the time.
You can then go back and install (one at a time) any of the tools. Evaluate consequences.
See Sceenshot