Here's how...

I typed in about:config into the location bar, scrolled down the list to dom.disable_image_src_set and clicked it to highlight it. I then Right clicked and selected Reset which turned it from True to False. And now I can see the maps.

I discovered the info after following many links on the Firefox help forum at http://forums.mozillazine.org/viewforum.php?f=38

Michael Ross