Hi Qwerty -
I am glad you were able to resolve the problem by removing Avast. We have solved many problems over the years by removing Avast, AVG, MacAfee and Norton.
I would run Avast clear to make sure you get it all out:
http://www.avast.com/en-us/uninstall-utility
Then type Security in Search to open Security Center and make sure Defender and all other security features are in a green state.
Finally run System File Checker to make sure any System Files Avast may have damaged are repaired. Follow Step 10 in this Checklist:
https://answers.microsoft.com/en-us/windows/for.... If it cannot repair the broken files then move on to Step 11 to do a Repair Install.
Let me know how this goes.