Hmmm...one of the ad networks that sometimes fills one of the side bar slots looks to be serving a massively wide ad at times. Premium members would never see, others may see it from time to time. Until I can contact them on Monday I've disabled that network. Should not happen again. Thanks for letting me know. Sorry for the inconvenience.
I saw it spaced like the image above earlier today for a short period, and later it looked fine.. I thought it was me..