Out of page interstitial not working with class element-hidden

When I tried to add an out-of-page interstitial tag on one of my site sections, the advert did display but I could not click through it. I could see the script being added to the page but the ad area was not clickable. The out-of-page ad was added via the context module to show only on some pages of the site.

Investigating this for a while (along with support calls to Google) the 'problem' seemed to be that the interstitial div wrapper had a class 'element-hidden' added to it. All the other tag wrappers for other ads that we have on the site did not have this extra class added to the div wrapper. Removing the extra class has solved the issue for us.

I know that the class must have been added for a reason but for us it causes the ad to be unclickable. Any help or explanation on what the right way to fix this would be much appreciated.

Thanks