Hi Amranen,
I'd like to understand the steps you took a bit better. Did you previously have Avast Antivirus installed or did you just install it for the first time after the error message? Or was the box unchecked in setup and you changed that?
If you could please provide a log file that would be great. That can be found in Computer, Program Data, Avast Software, Avast, Log. The file is SecureLine.txt
Thanks,
Davidek