This is exactly why I stopped upgrading CCleaner as soon as Avast bought them and will be removing it from all the PCs I manage. I used to use Avast's Antivirus and the popups were terrible. Not just the "Great Offers" but the news stories and everything else. It's annoying even when you're not playing a game.
There's plenty of other free antivirus and cleaner programs out there that don't do this crap.