Sorry before doing what you just suggested, the ad just started playing again as I was watching a youtube video. But several seconds in, it stopped playing. It seems like it starts playing around this time when I'm on the internet.
As I've said, there is no malware on the system...
I really do not know how to help you, I see nothing unusual in the logs. Maybe if you can to describe that issue more detailed, so I can understand what is going on.
Yesterday while I was on google chrome, the ads started playing and so when I closed the browser it stopped playing. So then I uninstalled google chrome and am using firefox now. I also uninstalled java after reading that it can also cause malware to come through. Not sure if that helps with these steps will help with the situation.