Could you please revert back to FusionMaps.js that our Download Pack has distributed?
I find that this is the line that you have modified:
swfNode += '<param name="movie" value="../LM-USA/'+ this.getAttribute('swf') +'" />';
which seem to fall heavy on all browsers which support <object> tag to load embeded objects in the HTML. It is trying to load the swf files from another path (hardcoded as ../LM-USA/ ) which, i fear does not exists or does not contain the required SWF files. There would be no problem with Firefox or browsers that use <embed> since that portion is not modified to use this hardcoded path.
The above line should be :
swfNode += '<param name="movie" value="'+ this.getAttribute('swf') +'" />';
I hope things will work fine and smooth now. It's a pleasure helping you out.