When I install Avast Premier (works fine with Avast free) I can't connect to the internet over any networks, neither cable nor wireless, unless I manually enter IP and DNS addresses in TCP/IP settings. I have Windows 10, and diagnosing says "One or more network protocols are missing from this computer". Fixing it automatically fails. I tried disabling NETBios over TCP/IP but it didn't help. Removing Avast fixes the issue.