I can't recreate the issue now (I could yesterday) - could the next person to see these do me a favour? Basically, when you close it, does a 'normal' banner ad appear on the page? Thanks!
It just happened to me, twice.
The Subaru advert appeared full page, with an X in the corner. Clicking on the X made it go away. It didn't go into a banner advert. I'm on a PC with Google Chrome.
The banner advert at the top was showing an advert for SAS Scandinavian Airways, and was displaying underneath the full page ad for Subaru.
I use AdBlock but have railforums on the safe list so the website can get income. I hope the full page ads don't continue, as I'll have to take it back off the safe list.