Moving backwards in a survey crashes

Hi there

Just installed and testing, and on a two-page survey after completing the first page and moving to the next I clicked the browser back button. The buttons below freeze as one says please wait forever.

In addition if i refresh the page the button changes back to "next" but cannot be pressed.

Using Joomla 3.1.5 and latest build of community surveys, nothing else on the site whatsoever. Running on wampserver

Many thanks