Show Legend not working in External Site

Folks,

a little different to Bryan's post just recently with his own issues of legends not showing. I'm running 4.1.2/2.2 HTML config, and I cannot get the icons/symbology to show on our external html facing sites - both tablet and handheld. The map service names show, but no images underneath them

I've set up a html viewer on the same internal site and it works fine.

Has anyone come across this before? and if so, know a way around it... I've tried to fiddler the request for images but it's not saying much, as it looks to be pre-canned/cached on load..??

cheers

Gareth