RJSdisplayed when using back button?

Given an action that responds to regular requests and XHR requests.

Eg. if request.xhr? then   render :update do |page| page.visual... end elsif !request.xhr? then   render :template => ... end

Using the browser back button to return to this page, firefox 2 will 'sometimes' display the raw javascript of the last XHR response and not the base page. Oddly, it doesn't happen if going back one page, but happens when going back several pages.

Maybe a browser issue, but wondering if anyone has any suggestions?

Many Thanks Andy Watts