I had a similar problem. I was using the "$. GetJSON" jQuery and everything worked perfectly in Firefox and Chrome.
But it did not work in IE. So I tried to directly access the URL of json, but in IE it asked if I wanted to download the file.
After much searching I saw that there must be a header in the result with a content-type, in my case, the content-type was:
header("Content-type: text/html; charset=iso-8859-1");
But when the page that made the request receives this json, in IE, you have to be specified SAME CONTENT-TYPE, in my case was:
$.getJSON (
"<? site_url php echo (" ajax / tipoMenu ")?>"
{contentType: 'text / html; charset = utf-8'},
function (result) {
hugs