They're not showing up for me in Firefox 27 on Mac OS X. If I remove the amazon part of the URL (leaving the domain as cdn.eventjoy.com) and use http instead of https, the image loads. On HTTPS, an Amazon certificate shows up and Amazon is sending some weird redirect XML.

I use (webkit-based) Epic, but on Firefox and Chrome it's working fine so I guess you don't need to worry! Sorry for the false alarm :)