Because to be one the safe side. the popups is from avast right?
could you provide a screenshot of that popup it usually gives more information.
if you follow the guide i have posted a malware expert will help you from there.
If the expert is not see nothing in the logs.
He will continue to help until this matter i solved.
It looks like you had a toolbar installed, but not uninstalled everything.
The log files of those scanners will tell why you get that message and what needs to be removed.