1] Remove Avast
2] Login as administrator (not as user with admin rights, that is something else)
3] Install Avast as ADMINISTRATOR.
Tried that. Same result, unfortunately.
Btw, when uninstalling, Avast does not remove its registry key,
and when installing again I got an error about insufficient
user rights. It turned out that even the Administrator account
could not overwrite the registry key that another Admin account
had created before. I had to give myself (Administrator) full permissions
to that key, then delete it, and then I could proceed installing.
Karl