Good to hear you at least know proper prevention methods! Time to teach the family :~)
Regarding why avast!, etc, won't work with your system, I honestly cannot answer that. There's clearly something on your system specifically that causes conflicts. For example, I see antivirus suites conflict with things often like wireless/network adapters (USB), backup software, encryption software, etc. Lots of possibilities. You'll need to do some troubleshooting if you really want to use avast! that much.
Regards,
Patrick