Derby Days <Com2Us> pop up keeps appearing, but only in that app.

Hi, just wondered if anyone has had or heard of a similar problem to this, and possible solutions. I, and other members of my family, run the Derby Days game app on a number of different Android platforms (all Jelly Bean). We all have the same problem, namely a pop up appearing, but only when that game is being run and not anything else. I have followed con2us' instructions and uninstalled the app, cleared the Google Play cache and re-installed the app, but to no effect.

The message we see on the pop-up is:

"The page at 'WHAT APPEARS TO BE A LINK TO AMAZON SHARED SPACE' says Play NOW!" Then there are "OK" and "Cancel" buttons

I always hit cancel. Does anyone know whatthis is and how to get rid of it?

Regards,
Robert