If you sign in using facebook, then there is something wrong with what is being retrieved from facebook. There is also an option to sign in using Google.
Personally I never use these alternative sign ins, I only use my avast account sign in for the forums and haven't had any issues. Secondly I don't sign out, so unless I have rebooted (infrequently), I just come back to the forums.
You must have used this email before, most likely on facebook as it appears like a partial element of your email has been for the user name.
The resolution is log on using your avast account credentials for pako7. Using a password manager could also help you a lot.