Robohelp 11 - updates to web page not visible in Firefox...ok in other browsers

Hi

We use Robohelp 11 to create help pages.

Often we notice that when we make changes and republish a page, the changes take a while to be visible in Firefox and Chrome, but tend to be immediately visible in Internet Explorer.

On this occasion we changed a page around two months ago (updated links for new embedded YouTube videos). I can see the new videos in Chrome and IE, but still see the old videos in Firefox 31.0, despite having cleared my cache.

Worried that users won't see updates.

Anyone experienced similar?

thanks

V