Some deets I forgot to add:
I'm running Chrome Version 29.0.1547.62 m, and Windows 7 SP 1 - 64 bit. I've noticed the pop-ups occur when I'm opening a new window, but I've never had the problem with these windows before. The pop-ups are visible (not black boxes like some have reported), and the site address appears in my History.
When using IE or firefox do they also occur? Post a pic of 1 please
Also, if the site addresses for these pop-ups appear in the history, is it always the same site or different sites? An example URL might be helpful for investigating this.