I have a form being AJAX'd in by jQuery on a page with multiple forms. I'm performing the following function, which is a wrapper for the $.ajax function:

function do_json_get(uri){
    var ret = '';
    var url = AJAX_URL + uri;

    $.ajax({
        type: 'GET',
        url: url,
        async: false,
        success: function(data) {
            ret = data.html;
        },
        dataType: 'json'
    });

    return ret;
}

When I go to the AJAX server directly (which is rendering the form in PHP), I get the raw JSON response - so I know the server is outputting to the browser, and the AJAX server is doing other things like setting the proper cookies, so I know that the connection is good (I get a 200 response code). Yet the data object is coming back null.

What else could I be missing?