Occasional page layout bug -- giant hole in banner-ad section

I've noticed this happening occasionally for the past few days.  The space where the "banner ad" appears, between the masthead and actual useful content, gets made extra large.  There's still a normal sized banner ad in place, but a lot of blank space below that.  A page refresh usually gets rid of it (and changes the banner ad).

Picture of Occasional page layout bug -- giant hole in banner-ad section
Occasional and bug, in the same sentence...

...This should be no trouble to sort out!

(we think it might be something with a campaign we started a few days ago...but...it shouldn't be doing that....which, makes for confusion)