Images don't show in Firefox

[Markv75]

Images in Featured Content Gallery do show in IE, but using Firefox I get a black box on http://hostallapinetina.com/en .
Please not the above website is a twin of http://casa-humboldt.com/en/ , where Firefox works fine.

I am puzzled, because the http://hostallapinetina.com/en is a "clone" of the second site.
Even when I disable all plugins the Firefox problems persists. This, and all I can think of I have tried.

Please advice.

Thanks a lot,
Mark

[Markv75]

Consider it solved!

The theme I have been using has option for showing its proprietary gallery (which doesn't work).
After I ticked "Featured Posts Enabled?
Uncheck if you do not want to show featured posts slideshow in homepage." FCG works fine in Firefox, too.